how to update all rows using text box

[dineshkumar123]

I retrieve all the row values from database into text box.But I could not Update it.It shows error message is
The variable name '@value' has already been declared. Variable names must be unique within a query batch or stored procedure.
Must declare the scalar variable "@keyValue" .

my code is here:

public partial class ECB_ECBConfiguration : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        DataTable dt = ECBDal.GetECBConfiguration();
       foreach(DataColumn col in dt.Columns) 
        {
            
            if (dt.Rows.Count > 0)
            {
                txtECBAddress.Text = dt.Rows[0]["Value"].ToString().Trim();
                txtECBServer.Text = dt.Rows[1]["Value"].ToString();
                txtECBEMailID.Text = dt.Rows[2]["Value"].ToString();
                txtECBContactNo1.Text = dt.Rows[3]["Value"].ToString();
                txtECBContactNo2.Text = dt.Rows[4]["Value"].ToString();
                txtECBContactNo3.Text = dt.Rows[5]["Value"].ToString();
                txtECBContactNo4.Text = dt.Rows[6]["Value"].ToString();
                txtECBContactNo5.Text = dt.Rows[7]["Value"].ToString();
            }
        }
    }
    protected void btnSave_Click(object sender, EventArgs e)
    {
        using (SqlConnection con = new SqlConnection(ConfigurationManager.AppSettings["MSSQLConnectionString"]))
        {
            SqlCommand cmd = new SqlCommand("UPDATE ECB_Configuration SET [Value] = @value where [Key] = @keyValue", con);
            con.Open();

            cmd.Parameters.AddWithValue("@value", txtECBAddress.Text);
            cmd.Parameters.AddWithValue("@value", txtECBServer.Text);
            cmd.Parameters.AddWithValue("@value", txtECBEMailID.Text);
            cmd.Parameters.AddWithValue("@value", txtECBContactNo1.Text);
            cmd.Parameters.AddWithValue("@value", txtECBContactNo2.Text);
            cmd.Parameters.AddWithValue("@value", txtECBContactNo3.Text);
            cmd.Parameters.AddWithValue("@value", txtECBContactNo4.Text);
            cmd.Parameters.AddWithValue("@value", txtECBContactNo5.Text);
            cmd.ExecuteNonQuery();
            ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('Record Updated Successfully')", true);
            con.Close();
        }

    }
    //protected void btnSave_Click(object sender, EventArgs e)
    //{
    //    ECBDal.SaveECBConfiguration();
        
    //}
    
     
}

[Rabbit]

Please use code tags when posting code or formatted data.

You defined value a bunch of times. And you never define the keyValue variable that you reference in your SQL.