SQL2008:ERROR: converting varchar to numeric problem

Question

While inserting it shows ERROR: converting varchar to numeric ..using c#.net


CREATE TABLE [dbo].[ITEMMASTER](
    [ID] [int] NULL,
    [ITEMCODE] [varchar](10) NULL,
    [ITEMDESCRIPTION] [varchar](50) NULL,
    [BRAND] [varchar](50) NULL,
    [ITEMGROUP] [varchar](50) NULL,
    [ITEMUNIT] [varchar](50) NULL,
    [PURCHASERATE] [numeric](12, 2) NULL,
    [MANUFACTURER] [varchar](50) NULL,
    [PURCHASEMRP] [numeric](12, 2) NULL,
    [OPENINGQTY] [numeric](12, 2) NULL,
    [OPENINGVALUE] [numeric](12, 2) NULL,
    [ISACTIVE] [bit] NULL,
    [REORDERLEVEL] [numeric](12, 2) NULL,
    [MINSTOCKQTY] [numeric](12, 2) NULL,
    [MAXSTOCKQTY] [numeric](12, 2) NULL,
    [VATPERCENT] [varchar](50) NULL
) ON [PRIMARY]



  if (txtItemCode.Text == "")
            {
                Response.Write("<script language='javascript'>alert('(*) fields are Required to Save the Data!!!');</script>");
            }
            else
            {
                Save_Record();
            }



  protected void Save_Record()
    {
        try
        {
            if (validate_data())
            {              
                string strSQL;
                string dbConn = ConfigurationManager.ConnectionStrings["CMC"].ConnectionString;
                SqlConnection sqlConn = new SqlConnection(dbConn);
                sqlConn.Open();
                strSQL = "INSERT INTO [ITEMMASTER](ITEMCODE,ITEMDESCRIPTION,BRAND,ITEMGROUP,ITEMUNIT,PURCHASERATE,MANUFACTURER,PURCHASEMRP,OPENINGQTY,OPENINGVALUE,REORDERLEVEL,MINSTOCKQTY,MAXSTOCKQTY,VATPERCENT)VALUES ('" + txtItemCode.Text + "','" + txtItemDescription.Text + "','" +DDLBrand.SelectedItem.ToString() + "','" +DDLItemGroup.SelectedItem.ToString() + "','" +DDLItemUnit.SelectedItem.ToString() + "','" +txtPurchaseRate.Text + "','" +DDLMfr.SelectedItem.ToString() + "','" +txtPurchaseMRP.Text + "','" +txtOpeningQuantity.Text + "', '" +txtOpeningValue.Text + "','" +txtReorderLevel.Text + "','" +txtMinStockQty.Text + "','" +txtMaxStockQty.Text + "','" +txtVAT.Text + "' )";

                //strSQL = "INSERT INTO [ITEMMASTER](ITEMCODE,ITEMDESCRIPTION,BRAND,ITEMGROUP,ITEMUNIT,PURCHASERATE,MANUFACTURER,PURCHASEMRP,OPENINGQTY,OPENINGVALUE,REORDERLEVEL,MINSTOCKQTY,MAXSTOCKQTY,VATPERCENT)VALUES ('" + txtItemCode.Text + "','" + txtItemDescription.Text + "','" +
                //  DDLBrand.SelectedItem.ToString() + "','" +
                //  DDLItemGroup.SelectedItem.ToString() + "','" +
                //  DDLItemUnit.SelectedItem.ToString() + "','" +
                // (string.IsNullOrEmpty(txtPurchaseRate.Text) ? "0.0" : txtPurchaseRate.Text) + "','" +
                //  DDLMfr.SelectedItem.ToString() + "','" +
                // (string.IsNullOrEmpty(txtPurchaseMRP.Text) ? "0.0" : txtPurchaseMRP.Text) + "','" +
                //  (string.IsNullOrEmpty(txtOpeningQuantity.Text) ? "0.0" : txtOpeningQuantity.Text) + "', '" +
                // (string.IsNullOrEmpty(txtOpeningValue.Text) ? "0.0" : txtOpeningValue.Text) + "','" +
                //  (string.IsNullOrEmpty(txtReorderLevel.Text) ? "0.0" : txtReorderLevel.Text) + "','" +
                //(string.IsNullOrEmpty(txtMinStockQty.Text) ? "0.0" : txtMinStockQty.Text) + "','" +
                //  (string.IsNullOrEmpty(txtMaxStockQty.Text) ? "0.0" : txtMaxStockQty.Text) + "','" +
                //  txtVAT.Text + "' )";

                SqlCommand cmdItemMaster = new SqlCommand(strSQL, sqlConn);
                cmdItemMaster.ExecuteNonQuery();              
                sqlConn.Close();
                Response.Write("<script language='javascript'>alert('Data Saved Successfully...');</script>");
                Load_Record();
               Record_Count();
            }
        }
        catch (Exception)
        {
            Response.Write("<script language='javascript'>alert('Error:Data Not Saved..!!!');</script>");
        }
    }




ABOVE IS MY TABLE AND QUERY... While inserting it shows ERROR: converting varchar to numeric .. Anyone pls help me......