Problem in for loop

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ASP.NET

I am having problem, i,e., if I choose an item from the dropdownlist and press the button, it enters into grid2 and if I again choose the same item and press the button, it does not enter into grid 2 showing a label "Item already exists" . Now that I choose a different item from the drop down list and press the button it is again allowed. Now if a select an item from the dropdown already present in the grid2 then ultimately it enters into Grid2 too which should not be allowed.

for (int i = 0; i < GridView2.Rows.Count; i++)
       {
           if (GridView2.Rows[i].Cells[11].Text==concat)
           {
               Label22.Visible = true;
               goto No;
              
           }
           else
           {
               break;
           }
       }

Label22.Visible = false;
        helper.InsertPlannedMaterialMasterRequest2(TextBox1.Text, TextBox2.Text, TextBox3.Text, TextBox6.Text, DropDownList2.SelectedValue, DropDownList3.SelectedValue, Convert.ToInt32(TextBox11.Text), DropDownList5.SelectedValue, Convert.ToInt32(DropDownList4.SelectedValue), Convert.ToInt32(TextBox13.Text), DropDownList6.SelectedValue,department, DateTime.Now,concat);
        LoadMasterRequests();
        LoadDetailRequests();
        LoadItems();
        BindData();
        BindData2();
        BindData3();
        goto d;
    No:
        Label22.Visible = true;
    d:
        TextBox6.Text = "";
        TextBox7.Text = "";
        TextBox11.Text = "";
        TextBox13.Text = "";