Delphi: Most Popular Articles
Windows Service applications take requests from client applications, process those requests, and return information to the client applications. They typically run in the background, without much user input. Services can be automatically started when the computer boots, can be paused and restarted, and do not show any user interface.
Symbolic constant names, hexadecimal values, and keyboard equivalents for the virtual key codes used by Windows.
Delphi tips, tricks and code snippets. Looking for a small code sample to help you make something big? It's here!
Executing and Running Applications and Files from Delphi Code.
Date/Time Delphi functions and procedures in RTL: rtl reference delphi programming time routines ordinal position date function
A Beginner's Guide to Delphi Programming. Free online programming tutorial / course for beginner developers. Focus on Borland Delphi.
Delphi's Pos function returns an integer specifying the position of the first occurrence of one string within another.
A Beginner's Guide to ASP.NET Programming for Delphi developers: Chapter 18. Find out what events (and in what order) are generated when ASP.NET receives a request for a Web Form. Learn about the ViewState - a technique ASP.NET uses to maintain page state changes across postbacks.
The concept of arrays in Delphi is simple: arrays allow us to refer to a series of variables by the same name and to use a number (an index) to tell them apart. Arrays have both upper and lower bounds, and the elements of the array are contiguous within those bounds.
Send email messages with attachments using Indy and Delphi. Full source code to a simple
Get familiar with the OnKeyDown, OnKeyUp, and onKeyPress Delphi event procedures to respond to various key actions or handle and process ASCII characters along with other special purpose keys.
String handling routines: rtl reference cr lf delphi programming dynamic array case sensitivity
Understanding and managing string data types in Delphi's Object Pascal. Learn about differences between Short, Long, Wide and null-terminated strings.
Whispering about reverse engineering Delphi applications: 'I have a Delphi program's .exe, can I decompile it and get the source?'. Page 3.
Exchanging Data over the Network using Delphi. In this article we'll examine two Delphi components: TServerSocket and TClientSocket, both designed to let you read and write information over a TCP/IP connection - thus enabling you to write network-aware applications.
The Windows Clipboard represents the container for any text or graphics that are cut, copied or pasted from or to an application. This article will show you how to use the TClipboard object to implement cut-copy-paste features in your Delphi application.
Everything you need to know about Delphi and the Extensible Markup Language. Find out about creating and parsing XML documents, look for parser components and more.
A Dynamic Link library, or DLL, is a collection of routines (small programs) that can be called by applications and by other DLLs. Using Delphi, we can write and use our own DLLs, and we can call functions in DLLs developed with other systems / by other developers. Find out how.
Multi-threading in Delphi lets you create applications that include several simultaneous paths of execution. When several threads are running in the application a question arises: how to update your GUI (user interface) as a result of a thread execution. The question lies in the TThread class Synchronize method.
Looking for a single-file, single-user database for your next Delphi application? Need to store some application specific data but you do not want to user the Registry / INI / or something else?
Sorting records in Delphi DBGrid. How to sort records in Delphi DbGrid by clicking on the column title. Plus: how to change the appearance of the selected column title to reflect the sort order. Even more: how to change the cursor when moving over the DBGrid column titles.
Let's enable uploading of binary files from a client browser to the web server in ASP.Net web applications. Delphi for .Net and ASP.NET provide an easy way to accept files from the client using HTMLInputFile ('HTML File Upload' HTML server control) and HTTPPostedFile classes.
The .INI files have a text-based file format for representing application configuration data in a format which is easily editable by humans and readable by a simple automatic parser. Learn how to use Delphi's TIniFile to read and write INI configuration files.
Here's how to store (and retrieve) a record (structure) value into a BLOB field in Delphi database applications.
There are situations when you want to display a list of strings to the user, for example in the list box control, but also have a way to store one more additional string (or event an object instance) along the one displayed to the user. Here's how when using Delphi.
The TStopWatch Delphi class implements a very accurate process execution timer and provides a set of methods and properties that you can use to accurately measure elapsed time.
An introduction to pointer data type in Delphi. What are pointers, why, when and how to use them.
Using Structured Query Language in Delphi.: tquery component delphi sql dbase tables interbase server component delphi
How Delphi uses standard Windows-format resource files: icons, bitmaps and cursors.
Free online database programming course for beginner Delphi developers. Focus on ADO techniques.
A free network (Internet / intranet) traffic (download / upload) monitor. Network traffic monitor allows you to quickly and easily examine the network usage of the local computer. Full Delphi source code included.
Accessing and managing MS Excel sheets with Delphi. How to retrieve, display and edit Microsoft Excel spreadsheets with ADO (dbGO) and Delphi. This step-by-step article describes how to connect to Excel, retrieve sheet data, and enable editing of data (using the DBGrid). You'll also find a list of most common errors (and how to deal with them) that might pop up in the process.
About.com's Delphi Programming site (http://delphi.about.com) proudly presents: free online programming tutorials for (beginner) Delphi developers!
Concise descriptions of Delphi versions and its history, along with a brief list of features and notes. Find out how Delphi evolved from Pascal to a RAD tool that can help you deliver high-performance, scalable applications ranging from desktop and database solutions to mobile and distributed applications for the Internet – not only for Windows but also for Linux and the .NET.
Coloring DBGrid. How to enhance the functionality of a TDBgrid component using colors
Loops allow you to execute a sequence of statements repeatedly, using a control condition or variable to determine when the execution stops. Delphi has three kinds of control loop: repeat statements, while statements, and for statements. Learn how to use loops in Delphi programming.
Contrary to most other Delphi data-aware controls, the DBGrid component has many nice features and is more powerful than you would have thought. The
A Simple example of Artificial Intelligence using Delphi. The article explores Delphi approach to AI, using the pebble picking game. A simple game is used to show how computer can learn by correcting mistakes.
Exchanging Data over the Network using Delphi. An introduction to sending data over the network using Delphi and Indy. The article focuses on sending / receiving record data and raw (binary) data using TCP connections.
Introduced in Delphi 2009, the TDictionary class, defined in Generics.Collections unit, represents a generic hash table type collection of key-value pairs. In Delphi, the TDictionary is defined as a hash table. Hash tables represents a collection of key-and-value pairs that are organized based on the hash code of the key. Hash tables are optimized for lookups (speed). When a key-value pair is added to a hash table, the hash of the key is computed and stored along with the added pair.
Here's how to show the contents of a MEMO (textual BLOB) field in a TDBGrid. Plus: how to enable editing of a TMemoField's contents using a separate window.
An introduction to Delphi Pascal. Before you start developing more sophisticated applications by using the RAD features of Delphi, you should learn the basics of the Delphi Pascal language.
Most often when programming in Delphi you don't need to dynamically create a component. If you drop a component on a form, Delphi handles the component creation automatically when the form is created. This article will cover the correct way to programmatically create components at run-time.
Learn about records, Delphi's data structure that can mix any of Delphi's built in types including any types you have created.
Here's an idea for your next application: create a
TColorButton - button with color properties. Full source code of the TColorButton Delphi component, an extension to the standard TButton control, with font color, background color and mouse over color properties.
Before you can call routines defined in DLL, you must import them. Functions exported from a DLL can be imported in two ways: by declaring an external procedure or function (static), or by direct calls to DLL specific API functions (dynamic). What should be used when: static or dynamic loading of DLLs in Delphi.
When you start programming in Delphi you might get errors like
Adding components to a DBGrid. How to place just about any Delphi control (visual component) into a cell of a DGBrid. Find out how to put a CheckBox, a ComboBox (drop down list box), a DateTimePicker (calendar) and even an Image inside the DBGrid.
Drop down list (DBLookupComboBox) inside a DBGrid - part 2. Here's how to place a DBLookupComboBox into a DBGrid. Create visually more attractive user interfaces for editing lookup fields inside a DBGrid - place a DBLookupComboBox into a cell of a DBGrid.
How to pass command-line parameters to your Delphi application and how to handle them.
The MD5 Message-Digest algorithm is used to check the integrity of files. Learn how to easily create a function to calculate the MD5 hash for a given file.
If you are up to creating a rock solid (OOP driven) Delphi application in a way that your code is maintainable, reusable, and flexible the OOP nature of Delphi will help you drive the first 70% of your route. Defining interfaces and implementing them will help with the remaining 30%.
Unlike regular .LNK shortcuts (that point to a document or an application), Internet Shortcuts point to an URL (web document). Here's how to create an .URL file, Internet Shortcut, using Delphi.
Need to highlight the row behind the mouse cursor in a DBGrid? Here's how to select (make active record) and highlight (change color, font, etc.) a row in a DBGrid as mouse moves around the grid.
If you need to implement some kind of authorization for your Delphi application you might want to display a login / password dialog *before* the main form is created and displayed to the user. In short, the idea would be to create, display, and destroy the
Learn how to read and manipulate XML documents with Delphi using the TXMLDocument component. Let's see how to extract the most current
How to obtain a computer's IP address by using the Socket API and Delphi's Pascal.
Screen RULER allows you to precisely measure anything on your computer screen. If you need to determine width and/or height of any object on your screen, Screen RULER is the tool to use. Transparency, units in pixels and millimeters and screen snapping are some of the features.
Coding the TScreen object, obtainer of all information about the current state of the screen in a Delphi application.
When creating Delphi database applications that are to be run on various machines, the connection to the data source should not be hard-coded in the executable. This article (with the sample project) shows how to store database connection parameters (server and database name) in Registry and how to build the ConnectionString dynamically.
A Beginner’s Guide to Delphi Programming: Chapter 1. What is Borland Delphi? Where to download a free version, how to install and configure it.
Storing more that just code in the application executable file. Working with resources from Delphi. How to embed a WAV, AVI and an MP3 file in a Delphi executable.
List of the file extensions created (and used) by Delphi and what they all mean. Plus, get to know what Delphi generated files should be stored in a source control system.
A selected collection of open source, free, and commercial Delphi components to help you add ZIP / UNZIP functionality to your application. Compressing and deflating files and directories in well-known formats like ZIP, RAR, TAR, GZIP, CAB will not longer be a missing piece in your Delphi projects!
What You Need to Know About Delphi Programming. The purpose of this page is to orient newcomers with an overview of some special features of the About Delphi Programming Web site.
Examining the life cycle of a Delphi Form - the central element of development in Delphi. See what's happening behind events OnCreate, OnActivate, OnShow, OnClose...
Taking a look at the use of standard HTML tags and elements and the use of server-side HTML controls - from a perspective of a Delphi developer.
The differences between a Delphi component Owner and its Parent explained. Plus: when to use the Controls and Component properties of a Delphi component.
When a combo box is in dropped down state Windows draws a list box type of control to display combo box items for selection. When the length (of a string) of items exceeds the width of the combobox, the items are displayed as cut-off! Here's how to ensure all ComboBox items are visible when drop down list is displayed.
When programming an event handler in Delphi (like the OnClick event of a TButton), there comes the time when your application needs to be busy for a while, e.g. the code needs to write a big file or compress some data. If you do that you'll notice that your application seems to be locked. Your form cannot be moved anymore and the buttons are showing no sign of life. It seems to be crashed. Application.ProcessMessages might come as a rescue, but you need to know its dark side!
Preparing to code with no barriers. See how to overcome the compiler version problem: compiling Delphi code for various Delphi versions.
One of the Delphi language features not found in other modern languages is the notion of sets. Delphi's set type is a collection of values of the same ordinal type. Learn about Delphi sets to better understand Delphi source code.
Understanding and using Borland Delphi Class procedures / functions. What they are and how to find a practical use for them.
Streams, streams, ... TStream. A stream is what its name suggests: a flowing river of data. A stream has a beginning, an end, and you're always somewhere in between of these two points. Learn about using the TStream class in Delphi: how to use stream objects to read from, write to, or copy information stored in a particular medium.
DBGrid with MultiSelect. Multiple row selection in Delphi DBGrid - providing the ability to select multiple records within the grid. A Beginner's Guide to Delphi Database Programming: Appendix A.
Delphi makes it easy to program dragging and dropping into our applications. You can even drag and drop from one form to another.
In Delphi, the XPath implementation is included in the xmldom.pas unit. Here's how to wrap XPath's selectNodes into IXMLNode.SelectNodes to get a collection of XML nodes into IXMLNodeList.
Placing Delphi applications in the System Tray in easy steps. The perfect place form programs that are left running for long periods of time with no user interaction.
Here's how to save a web page displayed inside a WebBrowser (TWebBrowser component) as a raw HTML file or into a single (MHT) file (MHTML format: web archive - single file) programmatically using Delphi.
Find out how to exploit the powers of the Sender parameter in Delphi: share event handlers and more.
With AsyncCalls you can execute multiple Delphi functions at the same time and synchronize them at every point in the function or method that started them. Here's an example project taking advantage of the thread pool implementation with CancelAll and WaitAll.
Generics, a powerful addition to Delphi, were introduced in Delphi 2009 as a new langage feature. Generics or generic types (also know as parametrized types), allow you to define classes that don't specifically define the type of certain data members. Get ready to use Generics.
Overview of dbExpress, along with a collection of tutorials and articles on building database applications using this data access technology.
Web Forms navigation in ASP.NET - Part 1. Exploring navigation techniques between Web Form pages: postbacks, direct navigation (using the <a> tag) and code-based navigation (using Server.Transfer and Response.Redirect).
I do not know when and where, but long time ago I read the following: "Delphi programming is the mutts
Learn how to create a powerful 'multiple document interface' application using Delphi. A Beginner's Guide to Delphi Programming: Chapter 11.
Free components, with code, made by the visitors of the About Delphi Programming community.
Adjusting Delphi's DBGrid column widths automatically. Here's a handy method to automatically fix the size of TDBGrid columns (at run-time) to fit the DBGrid width (remove the unfilled space at the right edge of the grid; and consequently remove the horizontal scroll bar) when the user resizes the container containing the grid.
While in most situations you will arrange all the controls on a Delphi form in a 'fixed' position, there are situations where you need to allow a user to change the placement and dimension of controls at run-time. Here's how to enable dragging and resizing controls with mouse, while the application is running.
Delphi's Copy function returns a substring of a string or a segment of a dynamic array.
Delphi's PosEx function returns an integer specifying the position of the first occurrence of one string within another, where the search starts at a specified position.
An overview of application development with Delphi, including creating a simple project, writing code, compiling and running a project. Also, find out how to ask Delphi for help.
Free online Borland Delphi OOP Course: Chapter Overview.
Working with common dialog boxes: Open and Save. How to create my own Notepad using Delphi. Part 1.
Stop. This is the one and only solution to file searching. Use Delphi to find any file in any directory and/or subdirectory that match a certain mask. Start searching.
Have you ever found yourself writing the same code over and over to perform some common task within event handlers? Yes? It's time for you to learn about programs within a program. Let's call those mini programs subroutines.
Learn how to show an Adobe Acrobat (.PDF) file in a Delphi application, which requires the free Acrobat ActiveX control.
Chapter seven of the free Delphi Database Course for beginners. Take a look at how you can take advantage of the TADOQuery component to boost your ADO-Delphi productivity.
This document describes what Windows hooks are and how to use them within a Delphi application.
Unfortunately, building applications includes coding. Regardless of how carefully you write/debug your program, it will be impossible to imagine every situation that can go wrong. Learn how to handle errors and exceptions in Delphi applications.
A Delphi function is a routine returning a value. A single value? Yes, No. No, a Delphi function can return multiple values and there are different ways how to achieve this goal. Either rely on VAR (by-reference) parameters or return a record, or something even more complex...
Web Forms navigation in ASP.NET - Part 2. Setting up the startup Web Form page for an ASP.NET application under IIS, exploring Server.Execute and deciding which navigation technique to use in various scenarios.
Learn how to send the WM_CopyData message between two Delphi applications to exchange information and make two applications communicate. The accompanying source code demonstrates how to send a string, record (complex data type) and even graphics to another application.
How to locate a TreeView node given by node text using Delphi
An overview of creating and using 'Borland Package Libraries' and how they compare with 'Dynamic Link Libraries' in creating smaller Delphi applications.
The Component Object Model (COM) enables programmers to develop objects that can be accessed by any COM-compliant application. Both OLE and ActiveX are based on COM.
Extending Delphi functions and procedures with default (optional) parameters and method overloading.
One way to make a computer program more robust and more amenable to change is to build it in layers. One might have a user interface layer that takes care of the interaction between the user and the program, an application layer that implements the operations required by the application, and a persistence layer that takes care of permanent storage of the data. Learn how to create 'The Three Layer' model in Delphi. This chapter discusses inheritance: deriving a new class from an existing one. Page 2.
The most basic splash screen is just an image (more precisely a form with an image) that appears in the center of the desktop screen when the application is loading (and gets hidden when the application is ready for usage).
An overview of VCL components allowing you to access a MySQL database from Delphi using standard data controls without using BDE/ADO/ODBC. Plus a few MYSQL related tools.
Delphi's LeftStr function returns a string containing a specified number of characters from the left side of a string.
TreeView with check boxes and radio buttons. Here's how to add check boxes and radio buttons to a TTreeView Delphi component. Give your applications a more professional and smoother look.
The ADPDBExplorer (About Delphi Programming Database Explorer) application allows you to connect to a Microsoft Access (MDB) database and/or SQL Server / MSDE database to explore a database structure, insert, edit or delete data. Features also include running 'free-hand' queries (select, insert, update, etc.) against the database using a simple query builder. A simple master-details relationships builder allows displaying and operating on joined tables.
A collection of 'Powered by Delphi' logos. Place them on your Web site, your Delphi application splash-screen, about box, help, documentation, and anywhere else you think it might be appropriate.
Implementing PING without using raw sockets. Implementing Internet pings using Delphi and the Icmp.dll.
Intercepting keyboard input for controls that cannot receive the input focus. Working with keyboard hooks in Delphi.
Delphi For Beginners: Interface, Implementation, Initialization, Finalization, Uses and other funny words.
What to keep in mind when scaling Delphi applications (forms) on different screen resolutions.
Full Delphi source code to a simple Chat application. Learn how UDP (User Datagram Protocol) broadcast can be used to find partners with unknown IP addresses in the network.
Delphi's StringReplace function returns a string in which a specified substring has been replaced with another substring.
Reading and writing to text (ascii) files using Delphi code. Find out how to read a line by line of a txt file and how to write some data back to the file.
The TTreeView Delphi component displays a hierarchical list of items - tree nodes. A node is presented by node text and an optional image. In real-world applications your tree nodes would need to carry more info: some more properties or even an entire custom object. How to?
Delphi For Beginners: Extend Delphi's built-in types by constructing your own types.
This first part demonstrates some of the best approaches to building components, and at the same time provides tips on deciding on the best base class to inherit from, using virtual declarations, the complexities of overriding, and so on.
In Delphi, the if statement is used to test for a condition and then execute sections of code based on whether that condition is True or False. Watchout for If Then Else traps if you are a beginner using nested if statements.
To speed up data processing, for example, fetching data from the database to create reports, you can add an additional thread to fetch and operate on the result (recordset). Learn about the traps in writing Multithreaded Delphi Database Queries with dbGo (ADO).
One of the keys to traditional Windows programming is handling the messages sent by Windows to applications. Handling Windows Messages the Delphi way!
Placing a TProgressBar into a TStatusBar. Here's how to add a status bar (or any other Delphi component) to a progress bar. Provide visual feedback of application's lengthy operation in the status area of a Delphi form.
Delphi's ExtractStrings function fills a string list with substrings parsed from a delimited list.
Controlling the number of application instances. In this article you'll learn how to 'run-once enable' a Delphi application that can check for its previous (running) instance. Along the process, several techniques of implementing such a check will be discussed; as well as how to bring your already running application to the foreground, if a user tries to run it 'one more time'. By the end of the article you'll have a copy-to-go code to control the behavior of your application's multiple instances: with the option to limit the number of running instances.
Delphi For Beginners: Object Pascal Variable Scope.
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Delphi's FormatDateTime function formats a TDateTime value to a string.
A regular expression (regex, regexp) is a string that describes or matches a set of strings, according to certain syntax rules. Regular expressions are used as a powerful and convenient way to recognise patterns in text. Delphi does not provide a regular expression library in the VCL, so you will need to use a third party VCL component. Here's a collection of regex libraries for Delphi.
Commenting Delphi code. Learn the art of helping yourself, when it comes to code maintenance. The purpose of adding comments to Delphi code is to provide more program readability using understandable description of what your code is doing.
Here's how to store TTreeView component items to XML (preserving the Text and other properties of a tree node) and how to populate a TreeView from an XML file.
Here's how to place an image into a cell of a TDBGrid. Enrich the visual presentation of data in Delphi database applications.
Working with units. A Beginner's Guide to Delphi Programming: Chapter 17. While developing a (large) Delphi application, as program becomes more complex, its source code can become very hard to maintain. In this article you will learn about creating your own code modules - Delphi code files that contain logically associated functions and procedures. Along the process we'll briefly discuss using Delphi's built-in routines and how to make all the units of a Delphi application cooperate.
Pressing the Tab key moves the input focus to next control and Shift-Tab to previous in the tab order of the form. When working with Windows applications, most users intuitively expect the Enter key to behave like a Tab key.
Listing Windows processes. Getting a list of Window processes and setting memory for return values using Delphi.
Delphi organizes applications into what is called projects. A project is made up of the visual interface along with the code that activates the interface. Each project can have multiple forms, allowing us to build applications that have multiple windows. Find out about Delphi's Project File in this article!
Chapter one of the free Delphi database online course. Delphi as the database programming tool, Data Access with Delphi...just a few words, Building a new MS Access database.
Drop down list inside a DBGrid - part 1. Here's how to place a drop down pick list into a DBGrid. Create visually more attractive user interfaces for editing lookup fields inside a DBGrid - using the PickList property of a DBGrid column.
An introduction to ASP.NET Web Server controls. Web Server controls are specifically designed to work with Web Forms pages. Find about the basic concepts, benefits and limitations of using Web Server controls in ASP.NET.
Creating a console mode application with Delphi; a text-mode program that runs without a graphical interface. Even more: see how to capture the output of a console application in a GUI Delphi program.
Concise descriptions of Delphi versions and its history, along with a brief list of features and notes. Find out how Delphi evolved from Pascal to a RAD tool that can help you deliver high-performance, scalable applications ranging from desktop and database solutions to mobile and distributed applications for the Internet not only for Windows but also for Linux and the .NET. Page 2.
How to register (and unregister) OLE controls such as dynamic-link library (DLL) or ActiveX Controls (OCX) files from a Delphi application.
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