【发布时间】：2012-08-08 10:21:14
【问题描述】：
我开发了一个 Windows 应用程序（C#.net）。我得到了例外，
对象引用未设置为对象的实例。
堆栈跟踪是
在 OnamVideoCable.Bill_Generate.btnBill_Click（对象发送者，EventArgs e) 在 C:\FinalOnam\CableOperatorSoftware\OnamVideoCable\OnamVideoCable\Bill 生成.cs：第 179 行
在 System.Windows.Forms.Control.OnClick(EventArgs e)
在 System.Windows.Forms.Button.OnMouseUp(MouseEventArgs 事件)
在 System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons 按钮，Int32 点击）
在 System.Windows.Forms.Control.WndProc(Message&m)
在 System.Windows.Forms.ButtonBase.WndProc(Message& m)
在 System.Windows.Forms.Button.WndProc(Message&m)
在 System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message&m)
在 System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
在 System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& 味精）
在 System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop（Int32 dwComponentID, Int32 原因, Int32 pvLoopData)
在 System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner（Int32 原因，ApplicationContext 上下文）
在 System.Windows.Forms.Application.ThreadContext.RunMessageLoop（Int32 原因，ApplicationContext 上下文）
在 OnamVideoCable.Program.Main() 中 C:\FinalOnam\CableOperatorSoftware\OnamVideoCable\OnamVideoCable\Program.cs:line 19
在 System.AppDomain._nExecuteAssembly(Assembly 程序集，String[] 参数）
在 Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
在 System.Threading.ExecutionContext.Run(ExecutionContext executionContext、ContextCallback 回调、Object 状态）
在 System.Threading.ThreadHelper.ThreadStart()
代码：
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
【问题讨论】：
-
访问时有些内容为空
-
请向我们展示 btnBill_Click 的代码。
-
哪个对象抛出异常？尝试初始化该特定对象。