How Can I Enable Design-Time Column Resizing in Custom Windows Forms Controls?

Enabling Design Support in Custom Controls

When creating custom controls, it's desirable to maintain the same functionality as their base controls. One such functionality is the ability to resize columns by dragging headers at design time. However, by default, custom controls do not inherit this behavior.

The Windows Forms designer uses dedicated designer classes for specific controls. The designer for a ListView, for example, is the internal System.Windows.Forms.Design.ListViewDesigner class. When placing a ListView on a user control, the default ControlDesigner is used instead, which doesn't provide the ability to drag column headers.

To remedy this, you can create a custom designer for the user control. By exposing the underlying ListView through a public property and applying the [DesignerSerializationVisibility] attribute, you can access and modify the ListView's properties at design time. Additionally, by applying the [Designer] attribute to the user control class, you can replace the default designer with your custom one.

Consider the following example:

using System;
using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;
using System.Windows.Forms.Design;   // Note: add reference required: System.Design.dll

namespace WindowsFormsApplication1 {
    [Designer(typeof(MyDesigner))]   // Note: custom designer
    public partial class UserControl1 : UserControl {
        public UserControl1() {
            InitializeComponent();
        }

        // Note: property added
        [DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]
        public ListView Employees { get { return listView1; } }
    }

    // Note: custom designer class added
    class MyDesigner : ControlDesigner {
        public override void Initialize(IComponent comp) {
            base.Initialize(comp);
            var uc = (UserControl1)comp;
            EnableDesignMode(uc.Employees, "Employees");
        }
    }
}

With this custom designer, the ListView within the user control can be clicked and designed just like a standalone ListView.

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