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• How do I supply a list of values to be chosen from a drop-down list at runtime for a specific type similar to enums?

  You have to implement a TypeConverter for your class and override the GetStandardValues and GetStandardValuesSupported method. In your override of GetStandardValuesSupported you have to return true. In your override of GetStandardValues you should return...

• How do I make a custom dialog droppable in the design surface like a component?

  Set the Designer attribute for your custom dialog to be ComponentDesigner (instead of the default ControlDesigner). That should make it droppable in the design surface as a component. Contributed from George Shepherd's Windows Forms FAQ

• How do I get notification when the user scrolls?

  You could override WndProc and listen for (0x114 WM_HSCROLL) and (0x115 WM_VSCROLL) messages (m.Msg will be set to the above values). These messages should be sent when the user scrolls. Contributed from George Shepherd's Windows Forms FAQ

• How do I add support for scrolling in a custom control?

  Windows Forms features a ScrollableControl. This will work in most cases where you know the exact dimensions of your control and scroll by pixel. See the MSDN Documentation for ScrollableControl for discussion how to use this control. Sometimes you may...

• How do I set AutoScrolling bounds, and do I use world or device coordinates?

  AutoScrollingMinSize is setup in device coordinates. If you are using a world coordinate system other than pixels this means that you have to translate between world and device coordinates before you set this value. You can use the Graphics.TransformPoints...

• How do I decide between using AutoScrolling and implementing custom scrolling?

  AutoScrolling, as provided by ScrollableControl.AutoScroll , does not allow you to dynamically control the scrolling interval. If you are drawing a complex control such as grid then you want to be able to scroll based on the current row height, column...

• How do I make a control automatically grow when the parent form is resized?

  Change the control's Anchor property so that it is anchored on all four sides. Please note that you can only have one control per form anchored in this manner, i.e., on all four sides. And other controls on the form should be anchored by their sides...

• What's the difference between the Anchor and Dock properties?

  G. G. Arun Ganesh discusses these properties in Working with Anchoring and Docking Properties on C# Corner .

• How do I prevent a TextBox from performing validation when the user clicks on the Cancel button?

  Say textBox1 and canelButton and the control names, then this is how you could do this: [C#] using System.ComponentModel; // Handler to the Validating event of the TextBox. private void TextBox_Validating( object sender, CancelEventArgs e ) { // Do this...

• How do I prevent a control from processing the Validating event when the user clicks on the Close box?

  One way is to add code to your Validating handler and only execute the validation routine if the mouse is in the client area. This will avoid the click on the title bar and its system menu. You might also want to add special handling for the tab key so...

• How do I invalidate a control including its non-client region?

  You can do so as follows in your Control: private void InvalidateWindow() { NativeMethods.RedrawWindow( Handle, IntPtr.Zero, IntPtr.Zero, 0x0400 | // RDW_FRAME 0x0100 | // RDW_UPDATENOW 0x0001 ); // RDW_INVALIDATE } Contributed from George Shepherd's...

• How do I support drag and drop of a hyperlink from IE into a Control?

  You can do this in the DragDrop event handler of your control: [C#] using System.IO; try { // Use e.Data.GetData("UniformResourceLocator") to get the URL byte[] contents = new Byte[ 512 ]; Stream ioStream= (Stream) e.Data.GetData( "FileGroupDescriptor"...

• How do I prevent a control from receiving focus when it receives a mouse click?

  You can set the control's Enabled property to false. This will prevent clicking but also gives the disabled look. There is a ControlStyles.Selectable flag that determines whether the control can get focus or not. But it does not appear to affect some...

• What is the DynamicProperties item on a control's Properties window?

  The (DynamicProperties) item that appears on the Properties window is used for setting property initialization through an XML file named app.config. Dynamic properties allow you to change property values without recompiling the application, for example...

• What is the best way to perform custom control initialization at runtime?

  When custom initialization is to be done during runtime on certain controls, the best way is to implement the ISupportInitialize interface in that control. Then the BeginInit method will be called as soon as the control gets created, and EndInit will...

• What's the IDropTarget interface for? Why would a control implement it?

  IDropTarget is a new interface that factors out the four drag drop methods - OnDragEnter, OnDragLeave, OnDragDrop, and OnDragOver - into an interface so that it can be implemented elsewhere. It is mostly an implementation detail.