null exception is occur

mohamed farhan

7y774Learn iOS Programming

Microsoft.Office.Interop.Excel._Application app = new Microsoft.Office.Interop.Excel.Application();

Microsoft.Office.Interop.Excel._Workbook workbook = app.Workbooks.Add(Type.Missing);

Microsoft.Office.Interop.Excel._Worksheet worksheet = null ;

worksheet = workbook.Sheets["sheet1"];

worksheet = workbook.ActiveSheet;

worksheet.Name = "Leave_Details";

for (int i = 1; i < dataGridView1.Columns.Count + 1; i++)

{

worksheet.Cells[1,i] = dataGridView1.Columns[i - 1].HeaderText;

}

for (int i = 0; i < dataGridView1.Rows.Count; i++)

{

for (int j = 0; j < dataGridView1.Columns.Count; j++)

{

worksheet.Cells[i + 2, j + 1] = dataGridView1.Rows[i].Cells[j].Value.ToString();

}

var saveFileDialoge = new SaveFileDialog();

saveFileDialoge.FileName = "Leave_Details";

saveFileDialoge.DefaultExt = ".xlsx";

if(saveFileDialoge.ShowDialog()==DialogResult.OK)

{

workbook.SaveAs(saveFileDialoge.FileName, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Microsoft.Office.Interop.Excel.XlSaveAsAccessMode.xlExclusive, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);

}

3 Replies

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Rajanikant Hawaldar7y ago
for example here I am creating object of employee class, Employee emp=new Employee(); through emp object we can access methods or properties. your your case emp object is null because your are not assigned memory using new operator to one object so you understand here we can't access methods or properties etc .
mohamed farhan7y ago
pls tell me clearly i am freasher

System.NullReferenceException was unhandled
HResult=-2147467261
Message=Object reference not set to an instance of an object.
Source=Leave Management
StackTrace:
at Leave_Management.Manager.btnexp_Click(Object sender, EventArgs e) in c:\Users\Ignovate003\Documents\Visual Studio 2013\Projects\Leave Management\Leave Management\Manager.cs:line 106
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.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.OnMessage(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(IntPtr 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 System.Windows.Forms.Application.Run(Form mainForm)
at Leave_Management.Program.Main() in c:\Users\Ignovate003\Documents\Visual Studio 2013\Projects\Leave Management\Leave Management\Program.cs:line 19
at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
InnerException:
Rajanikant Hawaldar7y ago
Hi Dear,

if object is not initialized then only this exeption will occur, Just keep breakpoint
at begin of method start debug and keep on mouse hover on each obj and see which obj
is null then allocate memory for it thats it.

Thanks