got the exception Object reference not set to an instance of an object
I have developed one windows application(C#.net).I got the exception, Object reference not set to an instance of an object.
stack trace is
at OnamVideoCable.Bill_Generate.btnBill_Click(Object sender, EventArgs e) in C:FinalOnamCableOperatorSoftwareOnamVideoCableOnamVideoCableBill Generate.cs:line 179
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ButtonBase.WndProc(Message& m)
at System.Windows.Forms.Button.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at OnamVideoCable.Program.Main() in C:FinalOnamCableOperatorSoftwareOnamVideoCableOnamVideoCableProgram.cs:line 19
at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
code:
private void btnBill_Click(object sender, EventArgs e) { int CustNo=0; int PayMonth; objB.OB = Convert.ToDouble(txtOB.Text);
if (ddCustSelect.Text == "All Customers")
{
try
{
DataTable dtCustNo = objCust.GetCustInfoForBill();
foreach (DataRow drCustNo in dtCustNo.Rows)
{
CustNo = Convert.ToInt32(drCustNo["CustNo"]);
DataTable dtR = new DataTable();
dtR=objR.GetLastReceiptInfo(CustNo);
if (dtR != null)
{
if (dtR.Rows.Count > 0)
{
DataRow drR = dtR.Rows[0];
//groupBox1.Visible = true;
//lblReceipt.Text = Convert.ToString(drR["RNo"]);
//lblPaidAmt.Text = Convert.ToString(drR["Amount"]);
// lbloutstand.Text = Convert.ToString(drR["Balance"]);
//lblMonthRate.Text = Convert.ToString(drR["MonthlyRate"]);
DateTime paydate = Convert.ToDateTime(drR["date"]);
//lblPayMonth.Text = Convert.ToString(drR["paydate"]);
PayMonth = paydate.Month;
objB.LastOut = Convert.ToDouble(drR["Balance"]);
total = calculate_bill(PayMonth, ddMonth.SelectedIndex + 1, Convert.ToDouble(drR["Balance"]), Convert.ToDouble(drR["MonthlyRate"]));
}
else
{
PayMonth = ddMonth.SelectedIndex + 1;
DataTable dtRate = objRate.GetExistCustRate(CustNo);
DataRow drRate = dtRate.Rows[0];
//total = calculate_bill(PayMonth, ddMonth.SelectedIndex + 1, 0, Convert.ToDouble(drRate["Total"]));
//objB.LastOut = 0;
total = Convert.ToDouble(drRate["Total"]);
objB.LastOut = total;
}
}
else
{
PayMonth = ddMonth.SelectedIndex + 1;
DataTable dtRate = objRate.GetExistCustRate(CustNo);
DataRow drRate = dtRate.Rows[0];
//total = calculate_bill(PayMonth, ddMonth.SelectedIndex + 1, 0, Convert.ToDouble(drRate["Total"]));
//objB.LastOut = 0;
total = Convert.ToDouble(drRate["Total"]);
objB.LastOut = total;
//MessageBox.Show("Table is null");
}
objB.CustNo = Convert.ToInt32(CustNo);
objB.Month = ddMonth.Text;
objB.Year = ddYear.Text;
objB.Total = total;
DataTable dtBill = new DataTable();
dtBill = objB.checkBill();
if (dtBill != null)
{
if (dtBill.Rows.Count > 0)
{
// MessageBox.Show("Bill is Already Generated");
continue;
}
else
{
objB.GenerateBill();
}
}
else
{
//MessageBox.Show("2nd table is null");
objB.GenerateBill();
}
}
MessageBox.Show("Bill is generated");
}
catch (Exception ex)
{
// MessageBox.Show(ex.Message + CustNo);
throw ex;
}
}
if (ddCustSelect.Text == "Single Customer")
{
try
{
//panelSingle.Visible = true;
// groupBox1.Visible = true;
objB.CustNo = Convert.ToInt32(ddCustNo.Text);
objB.Month = ddMonth.Text;
objB.Year = ddYear.Text;
objB.Total = Convert.ToDouble(lblTotalBill.Text);
if (lbloutstand.Visible)
{
objB.LastOut = Convert.ToDouble(lbloutstand.Text);
}
else
{
objB.LastOut = objB.Total;
}
DataTable dtBill = objB.checkBill();
if (dtBill != null)
{
if (dtBill.Rows.Count > 0)
{
MessageBox.Show("Bill is Already Generated");
}
else
{
if (objB.GenerateBill())
{
MessageBox.Show("Bill is generated..");
}
else
{
MessageBox.Show("Error while generating bill");
}
}
}
else
{
MessageBox.Show("2nd table null");
}
}
catch(Exception)
{
}
}
}----this is line no 179
So look carefully at (or near - the numbers can be a few out) line 179 in
at OnamVideoCable.Bill_Generate.btnBill_Click(Object sender, EventArgs e) in C:FinalOnamCableOperatorSoftwareOnamVideoCableOnamVideoCableBill Generate.cs:line 179
Something in there is null. Add a breakpoint and use the debugger. Either check for the null, or fix whatever is making it null unexpectedly. I can't tell you what - I can't see your code!
查看Generate.cs：第179行，检查你在这一行中使用的变量，其中一个是null
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