public partial class RadForm1 : Telerik.WinControls.UI.RadForm
 {
     public RadForm1()
     {
         RadGridLocalizationProvider.CurrentProvider = new MyRadGridLocalizationProvider();
         InitializeComponent();

         this.radGridView1.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;
         this.radGridView1.EnableFiltering = true;
         this.radGridView1.MasterTemplate.ShowFilteringRow = true;

         this.radGridView1.FilterExpressionChanged += this.RadGridView1_FilterExpressionChanged;

         this.radGridView1.ContextMenuOpening += this.RadGridView1_ContextMenuOpening;
     }

     private void RadGridView1_ContextMenuOpening(object sender, ContextMenuOpeningEventArgs e)
     {
         if (e.ContextMenu.Items[0] is RadFilterOperationMenuItem)
         {
             foreach (RadMenuItemBase menuItem in e.ContextMenu.Items)
             {
                 if (string.Equals("Starts with", menuItem.Text))
                 {
                     menuItem.Text = "Does not starts with";
                 }
             }
         }
     }

     private void RadGridView1_FilterExpressionChanged(object sender, FilterExpressionChangedEventArgs e)
     {
         var ex = e.FilterExpression;
         if (ex.Contains("LIKE") && ex.Contains("%"))
         {
             this.radGridView1.FilterExpressionChanged -= this.RadGridView1_FilterExpressionChanged;
             e.FilterExpression = ex.Replace("LIKE", "NOT LIKE");
             this.radGridView1.FilterExpressionChanged += this.RadGridView1_FilterExpressionChanged;
         }
     }

     private void RadForm1_Load(object sender, EventArgs e)
     {
         this.customersTableAdapter.Fill(this.nwindDataSet.Customers);

     }
 }
 public class MyRadGridLocalizationProvider : RadGridLocalizationProvider
 {
     public override string GetLocalizedString(string id)
     {
         switch (id)
         {
             case RadGridStringId.FilterOperatorStartsWith:
                 return "Does not starts with";
             default:
                 return base.GetLocalizedString(id);
         }
     }
 }