PropertyGridExtensions.cs

using System;
using System.Reflection;
using System.Windows.Forms;

/// <summary>
/// Extension methods for System.Windows.Forms.PropertyGrid.
/// </summary>
public static class PropertyGridExtensions
{
    /// <summary>
    /// Move the PropetyGrid's splitter to the specified position.
    /// </summary>
    /// <param name="propertyGrid">The PropertyGrid that will have its splitter moved.</param>
    /// <param name="position">The new position of the splitter.</param>
    public static void MoveSplitterTo(this PropertyGrid propertyGrid, int position)
    {
        // This is a bit of a hack... There is an internal class known as 
        // System.Windows.Forms.PropertyGridInternal.PropertyGridView, which
        // contains the 'MoveSplitterTo' method. We'll use reflection to call
        // this MoveSplitterTo method!

        // The System.Windows.Forms.PropertyGridInternal.PropertyGridView is 
        // always the 3rd Control in the PropertyGrid's Control collection.
        Control propertyGridView = propertyGrid.Controls[2];
        Type propertyGridViewType = propertyGridView.GetType();

        // The method we want to call is defined as: private void MoveSplitterTo(int xpos)
        BindingFlags flags = BindingFlags.Instance | BindingFlags.NonPublic;
        MethodInfo methodInfo = propertyGridViewType.GetMethod("MoveSplitterTo", flags);
        if (methodInfo != null)
            methodInfo.Invoke(propertyGridView, new object[] { position });
    }
}