How to insert more then one record from grdviw to SQL server in ASP.NET

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C#

Hi everybody, i have two table, saleorder,and itemorder, i can insert in both table from on click, but when i want to insert more then one record from gridview, it give me this error,(Procedure or function insertsale has too many arguments specified.) can any body help me please, below is my code

What I have tried:

SqlCommand cmd = new SqlCommand("insertsale");

cmd.Parameters.AddWithValue("@CustomerId", DropDownList3.SelectedValue);
//cmd.Parameters.AddWi
cmd.Parameters.AddWithValue("@SoDate", Convert.ToDateTime(TextBox13.Text));
cmd.Parameters.AddWithValue("@MadeBY", int.Parse(DropDownList4.SelectedValue));
cmd.Parameters.AddWithValue("@SubTotal", TextBox1.Text);
cmd.Connection = mycon;

cmd.CommandType = CommandType.StoredProcedure;

DataTable dt1 = (DataTable)Session["DataTable"];
for (int i = 0; i < dt1.Rows.Count; i++)
{

cmd.Parameters.AddWithValue("@ItemID", dt1.Rows[i]["ItemID"].ToString());
cmd.Parameters.AddWithValue("@Quantity", dt1.Rows[i]["Quantity"].ToString());
cmd.Parameters.AddWithValue("@Rate", dt1.Rows[i]["Rate"].ToString());
cmd.Parameters.AddWithValue("@Total", dt1.Rows[i]["total"].ToString());

}


mycon.Open();
cmd.ExecuteNonQuery();
mycon.Close();

and my storprocdure is
StoredProcedure [dbo].[insertsale] Script Date: 3/31/2016 9:00:27 AM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER procedure [dbo].[insertsale]
(
@CustomerID int,
@SoDate datetime,
@SubTotal varchar(50),
@MadeBY varchar (50),
@ItemID int,
@Quantity varchar(50),
@Rate varchar(50),
@Total varchar(50)
)
as
begin

insert into SalesOrder(CustomerId,SoDate,SubTotal,MadeBY)
values (@CustomerID,@SoDate,@SubTotal,@MadeBY)

insert into OrderItems(SalesID,ItemID,Quantity,Rate,Total)
values (SCOPE_IDENTITY(),@ItemID,@Quantity,@Rate,@Total)

end