Using the standard Microsoft .NET 2.0 WinForms PropertyGridControl control, I was looking for a way to set the size of the two columns (one for the labels, one for the values) so that I can control better how the values are displayed.

After some research with ILSpy on the .NET sources, I found a way to use with reflection. The following helper method can be used for this task:

public static void ResizePropertyGridSplitter(
    PropertyGrid propertyGrid,
    int labelColumnPercentageWidth)
{
    var width =
        propertyGrid.Width*(labelColumnPercentageWidth/100.0);

    // Go up in hierarchy until found real property grid type.
    var realType = propertyGrid.GetType();
    while (realType!=null && realType != typeof(PropertyGrid))
    {
        realType = realType.BaseType;
    }

    var gvf = realType.GetField(@"gridView",
        BindingFlags.NonPublic |
        BindingFlags.GetField |
        BindingFlags.Instance);
    var gv = gvf.GetValue(propertyGrid);

    var mtf = gv.GetType().GetMethod(@"MoveSplitterTo",
        BindingFlags.NonPublic |
        BindingFlags.InvokeMethod |
        BindingFlags.Instance);
    mtf.Invoke(gv, new object[] { (int)width });
}

Call the function and pass your PropertyGrid instance and width values between e.g. 10 and 90 to resize the first column to the given percentage value.

E.g.:

ResizePropertyGridSplitter( myPropGrid, 75 );

If you specify a too small or too large value, the PropertyGrid seems to use the minimum/maximum possible, based on your passed value.