Accessing Child Templates
You can programmatically access your child templates using MasterTemplate.Templates collection. For example, use the following code to set the AutoSizeColumnsMode to Fill in the first child template :
this.radGridView1.MasterTemplate.Templates[0].AutoSizeColumnsMode = Telerik.WinControls.UI.GridViewAutoSizeColumnsMode.Fill;
Me.RadGridView1.MasterTemplate.Templates(0).AutoSizeColumnsMode = Telerik.WinControls.UI.GridViewAutoSizeColumnsMode.Fill