中继器中的文本框值并保存

Question

I have a code here that gets a transaction number on a search bar and show it on the page. I also have 2 textbox wherein the client will enter the price payed and the OR No of the receipt. However, I am getting an error

"Object reference not set to an instance..."

.ASPX

<form id="form1" runat="server">
<div>
<asp:Repeater ID="rptrCashierTable" runat="server">
    <ItemTemplate>
        <div>
            <h1 align="center">Transaction Number: <label><%# Eval("TXNNo") %></label>

         <h2>Name:<label><%# Eval("FName") %></label>
         <label><%# Eval("MName") %></label>
         <label><%# Eval("LName") %></label></h2>             
         <h2>Contact Number: <label><%# Eval("MOBILE") %></label></h2>
         <h2>Product Ordered: <label><%# Eval("PName") %></label></h2>
         <h2>Product ID:<label><%# Eval("ProductID") %></label></h2>
         <h2>Price: 
             <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox></h2>
         <h2>OR No.: 
             <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox></h2>
                <asp:Button ID="Button1" runat="server" Text="Submit" OnClick="btn_Update" />
        </div>
    </ItemTemplate>
</asp:Repeater>
</div>
</form>

.CS

public partial class TransactionDetails : System.Web.UI.Page
{
    SQLQuery sql = new SQLQuery();
    DataSet ds = new DataSet();

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            BindCasierTable();
        }

    }
    private void BindCasierTable()
    {            
        string TransctID = Request.QueryString["TXNNo"];
        ds = sql.dsGetClientDetails(TransctID);

        rptrCashierTable.DataSource = ds;
        rptrCashierTable.DataBind();
    }

    protected void btn_Update(object sender, EventArgs e)
    {


        foreach (RepeaterItem item in rptrCashierTable.Items)
        {                           

            if (item.ItemType == ListItemType.Item)
            {
                var txtPrice = item.FindControl("TextBox1") as TextBox;
                var txtORNo = item.FindControl("TextBox2") as TextBox;
                string TXNNo = Request.QueryString["TXNNo"];
                ds = sql.dsAddPayment(txtPrice.Text, txtORNo.Text, TXNNo);
                txtPrice.Text = string.Empty;
                txtORNo.Text = string.Empty;
                BindCasierTable();
            }


        }
    }
}

I am using MSSQL 2008 and stored procedure. I just want to update and put the Price payed and OR number to their respective field.

Answer 1

That error message means you are assigning something with null value. I guess the error pops out here:

string TransctID = Request.QueryString["TXNNo"]

you should check if its null first:

if(Request.QueryString["TXNNo"]!=null)
{
 // make the assignation here
}