Making a custom control's property input like that of a multiline textbox

Question

Say I have attribute "Address", how can I make it's input in the form designer's property box like that of a text box's text input, like so:

?

Answer 1

Decorate your Address property with an EditorAttribute referencing the MultilineStringEditor class:

using System.ComponentModel;
using System.Drawing.Design;

[Editor("System.ComponentModel.Design.MultilineStringEditor, System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a",
    typeof(UITypeEditor))]
public string Address
{
    get;
    set;
}

Answer 2

This happens through a "designer". For System.Windows.Forms.TextBox that designer is:

[Designer("System.Windows.Forms.Design.TextBoxDesigner, System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"), SRDescription("DescriptionTextBox"), ComVisible(true), ClassInterface(ClassInterfaceType.AutoDispatch)]

If you want to view its source code, open up .NET Reflector, Open Cache... System.Design, navigate (or search) to System.Windows.Forms.Design.TextBoxDesigner .

UPDATE: Since 2014, the .NET Core is open-source, check out the official repository site