要设置 EnableLinqExpressions="false"，搞了3,4个小时没反应，就是没有设置这个

 

 Protected Sub btnSearch_Click(sender As Object, e As EventArgs)

        RadGrid1.MasterTableView.FilterExpression = "([" + "UserName" + "] ='" + "xiaoming" + "')"

        RadGrid1.MasterTableView.Rebind()

    End Sub