how to insert gridView data into Database

i want to add the grid view data in data base in grid view i select the all item now all the item i want to save in database can anyone help me here is my gridview code

 

 

protected void btnSubmit0_Click(object sender, EventArgs e)
{


DataTable dt = new DataTable();

dt.Columns.Add("Product");
dt.Columns.Add("Qunatity");
dt.Columns.Add("UnitPrice");
dt.Columns.Add("total");


DataRow dr = null;
if (ViewState["sale"] != null)
{
for (int i = 0; i < 1; i++)
{
dt = (DataTable)ViewState["sale"];
if (dt.Rows.Count > 0)
{
dr = dt.NewRow();
dr["Product"] = ddlProduct.SelectedValue;
dr["Qunatity"] = Convert.ToInt32(txtQuantity.Text);
dr["UnitPrice"] = Convert.ToInt32(TxtUnitPrice.Text);
dr["total"] = Convert.ToInt32(TxtTotal.Text);


dt.Rows.Add(dr);
GridView1.DataSource = dt;
GridView1.DataBind();

}

}
}

else
{
dr = dt.NewRow();
dr["Product"] = Convert.ToInt32(ddlProduct.SelectedValue);
dr["Qunatity"] = Convert.ToInt32(txtQuantity.Text);
dr["UnitPrice"] = Convert.ToInt32(TxtUnitPrice.Text);
dr["total"] = Convert.ToInt32(TxtTotal.Text);


dt.Rows.Add(dr);
GridView1.DataSource = dt;
GridView1.DataBind();

}
ViewState["sale"] = dt;

} 

 

 

and here is my database insert code