Object must implement IConvertible
<p>Object must implement IConvertible. 
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. </p>

<blockquote>
  <p>Exception Details: System.InvalidCastException: Object must implement
  IConvertible.</p>
  
  <p>Error Detail Line 279:<br>
  da.InsertCommand.Parameters.Add("@Total", SqlDbType.Int).Value =
  txttotal.Text; Line 280:        con1.Open(); Line 281:<br>
  da.InsertCommand.ExecuteNonQuery();</p>
</blockquote>

<p>Code</p>

<pre><code>SqlDataAdapter da = new SqlDataAdapter();
        da.InsertCommand = new SqlCommand("Insert Into customer_order(ProductID,product_Name,Product_Type,Weight,Unit_Price,No_Of_Master_Pack,Master_Pack_Price,Quantity,Total)VALUES(@ProductID,@product_Name,@Product_Type,@Weight,@Unit_Price,@No_Of_Master_Pack,@Master_Pack_Price,@Quantity,@Total)", con1);
        da.InsertCommand.Parameters.Add("@ProductID",SqlDbType.VarChar).Value=DropDownList3.SelectedItem;
        da.InsertCommand.Parameters.Add("@product_Name",SqlDbType.VarChar).Value=DropDownList2.SelectedItem;
        da.InsertCommand.Parameters.Add("@Product_Type", SqlDbType.VarChar).Value = DropDownList1.SelectedItem;
        da.InsertCommand.Parameters.Add("@Weight",SqlDbType.Int).Value=txtwgt.Text;
        da.InsertCommand.Parameters.Add("@Unit_Price",SqlDbType.Int).Value=txtmrpsinglepack.Text;
        da.InsertCommand.Parameters.Add("@No_Of_Master_Pack",SqlDbType.Int).Value=txtnoofmasterpack.Text;
        da.InsertCommand.Parameters.Add("@Master_Pack_Price",SqlDbType.Int).Value=txtmrpmaster.Text;
        da.InsertCommand.Parameters.Add("@Quantity",SqlDbType.Int).Value=txtquantity.Text;
        da.InsertCommand.Parameters.Add("@Total", SqlDbType.Int).Value = txttotal.Text;
        con1.Open();
        da.InsertCommand.ExecuteNonQuery();
</code></pre>
