The variable name '@VarName' has already been declared Issue
<p>I am inserting multiple items into table based on a selection from drop down list.  When I select one item from the drop down then everything works fine but when I select multiple items then I get this error</p>

<pre><code>The variable name '@CompName' has already been declared. Variable names must be unique within a query batch or stored procedure.
</code></pre>

<p>what am i doing wrong?  thanks
here is my code</p>

<pre><code>protected void DV_Test_ItemInserting(object sender, DetailsViewInsertEventArgs e)
    {
        foreach (ListItem listItem in cblCustomerList.Items)
        {
            if (listItem.Selected)
            {
                string Name= listItem.Value;
                sqlcon.Open();
                string CompName= ((TextBox)DV_Test.FindControl("txtCompName")).Text.ToString();
                string Num = ((TextBox)DV_Test.FindControl("txtNum")).Text.ToString();
                SqlCommand cmd = new SqlCommand("select CompNamefrom MyTable where CompName= '" + CompName+ "' and Num = '" + Num + "' and Name= '" + Name+ "'    ", sqlcon);
                SqlDataReader dr = cmd.ExecuteReader();
                if (dr.Read())
                {
                    lblmsg.Text = "Not Valid";
                }
                else
                {
                    dr.Close();

                    sqlcmd.CommandText = "INSERT INTO MyTable(CompName, Num, Name) VALUES(@CompName, @Num, @Name)";
                    sqlcmd.Parameters.Add("@CompName", SqlDbType.VarChar).Value = CompName;
                    sqlcmd.Parameters.Add("@Num", SqlDbType.VarChar).Value = Num;
                    sqlcmd.Connection = sqlcon;                 
                    sqlcmd.ExecuteNonQuery();
                    DV_Test.ChangeMode(DetailsViewMode.Insert);
                    sqlcon.Close();
                }
                sqlcon.Close();               
            }

         }
 }
</code></pre>
