How can I handle this error?

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hi

i have this error:

C#

Object reference not set to an instance of an object. 

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error: 


Line 2420:                Else
Line 2421:                    Throw ex
Line 2422:                End If
Line 2423:
Line 2424:            Finally 

Source File: C:\Istg\Final version 941211\IstgVersions\IstgVersions\workflow\Pages\Compose.ascx.vb    Line: 2422 

Stack Trace: 


[NullReferenceException: Object reference not set to an instance of an object.]
   IstgWebApp.clsWorkflowCompose.Page_Load(Object sender, EventArgs e) in C:\Istg\Final version 941211\IstgVersions\IstgVersions\workflow\Pages\Compose.ascx.vb:2422
   System.Web.UI.Control.LoadRecursive() +71
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3178

///////////////////////

my vb code is here:

If Request.Params.Get("__EVENTTARGET") = "Confirm" Then
                    Confirm()
                ElseIf Request.Params.Get("__EVENTTARGET") = "save" Then
                    SaveDraft()
                ElseIf Request.Params.Get("__EVENTTARGET") = "ChangeEditor" Then
                    LoadEditor()
                ElseIf Request.Params.Get("__EVENTTARGET") = "ddlDocumentTemplateRef_DropDown_IndexChange" Then
                    ddlDocumentTemplateRef_IndexChanged()
                ElseIf Request.Params.Get("__EVENTTARGET") = "ddlGroup_DropDown_IndexChange" Then
                    ddlGroup_IndexChanged()
                End If
                divScript.InnerHtml = ""


            Catch ex As Exception
                If ex.Message = "Could Not Open The Letter" Then
                    Response.Write("<script>alert('اشکال در باز کردن نامه');</script>")
                Else
                    Throw ex
                End If

            Finally

            End Try

<pre lang="vb">

///////////////////

thanks for your help

What I have tried:

i want to solve this problem. please help me to do that

Posted 24-Mar-16 9:26am

Member 12414906

Updated 24-Mar-16 19:37pm

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OriginalGriff · Answer 1 · 2016-03-24T12:09:00

This is one of the most common problems we get asked, and it's also the one we are least equipped to answer, but you are most equipped to answer yourself.

Let me just explain what the error means: You have tried to use a variable, property, or a method return value but it contains null - which means that there is no instance of a class in the variable.
It's a bit like a pocket: you have a pocket in your shirt, which you use to hold a pen. If you reach into the pocket and find there isn't a pen there, you can't sign your name on a piece of paper - and you will get very funny looks if you try! The empty pocket is giving you a null value (no pen here!) so you can't do anything that you would normally do once you retrieved your pen. Why is it empty? That's the question - it may be that you forgot to pick up your pen when you left the house this morning, or possibly you left the pen in the pocket of yesterdays shirt when you took it off last night.

We can't tell, because we weren't there, and even more importantly, we can't even see your shirt, much less what is in the pocket!

Back to computers, and you have done the same thing, somehow - and we can't see your code, much less run it and find out what contains null when it shouldn't.
But you can - and Visual Studio will help you here. Run your program in the debugger and when it fails, VS will show you the line it found the problem on. You can then start looking at the various parts of it to see what value is null and start looking back through your code to find out why. So put a breakpoint at the beginning of the method containing the error line, and run your program from the start again. This time, VS will stop before the error, and let you examine what is going on by stepping through the code looking at your values.

But we can't do that - we don't have your code, we don't know how to use it if we did have it, we don't have your data. So try it - and see how much information you can find out!

Member 12392991 · Answer 2 · 2016-03-24T19:37:00

please check the parameter in the first line for null if it is not null then process the further code otherwise do whatever you want to do.

if(!String.IsNullorEmpty(Request.Params.Get("__EVENTTARGET")) should be checked against null value. i think it is not pointing out any object so your program is throwing the error.you may use this code line for every parameter that you are getting using Get before processing .

null reference error is a common error . so programmer should always have a check for null values .

How can I handle this error?

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