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Same function with same arguments, from same dll reference (same path, same file), working for one .NET project, but not for an other

The .NET project that works is on .NET framework 4.6.1. The one that does not work is on .NET framework 4.7.2.
This is the Function:
return DAL.DALGeneral.SelectScalar("GetYearName", new Dictionary<string, object>() { { "Year", year } }).ToString();
This is the Error message:
[NullReferenceException: Object reference not set to an instance of an object.]
DAL.DALGeneral.GetConnectionString(String DataBase) +83
DAL.DALGeneral.SelectScalar(String spName, Dictionary`2 parameters, String DataBase, String ConnectionString) +123
OnlineYudGimelDaledSignIn.Models.LookUp.GetYearName(Int32 year) in C:\Users\giln\source\repos\OnlineYudGimelDaledSignIn\OnlineYudGimelDaledSignIn\Models\LookUp.cs:58
OnlineYudGimelDaledSignIn.Site.Page_Load(Object sender, EventArgs e) in C:\Users\giln\source\repos\OnlineYudGimelDaledSignIn\OnlineYudGimelDaledSignIn\Site.Master.cs:29
System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +52
System.Web.UI.Control.OnLoad(EventArgs e) +97
System.Web.UI.Control.LoadRecursive() +61
System.Web.UI.Control.LoadRecursive() +134
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +693
Im stumped as to why, the same function with the same arguments works from an other project.
I tried sending different arguments to the function and i get different error, but i need it to be these arguments.

Ok, so i had a missing connection string in the web.config file in the second project. I didn't realize dll reference uses the current project config file, and not his own somehow.

Debugging compiled function in ASP .NET

I have a website I believe to be in ASP .NET, which is throwing an exception System.NullReferenceException: Object reference not set to an instance of an object.. Stack trace shows as follows:
[NullReferenceException: Object reference not set to an instance of an object.]
SomeScript.getConnection() +32
SomeScript.buildGridData() +299
SomeScript.Page_Load(Object sender, EventArgs e) +92
System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +43
System.EventHandler.Invoke(Object sender, EventArgs e) +0
System.Web.UI.Control.OnLoad(EventArgs e) +91
System.Web.UI.Control.LoadRecursive() +74
System.Web.UI.Control.LoadRecursive() +163
System.Web.UI.Control.LoadRecursive() +163
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2603
Same error is occurring for basically all pages of the site which request data, with just the SomeScript in above stack trace alternating for the loading script.
Environmental changes have only been in changing password for a remote SMTP server the site uses for mailing out, but site was continuing to load fine after that change was made.
My feeling is that these errors with the getConnection() method started occurring after a user tried to use said SMTP mailing function within the website and received an error (I was not able to capture the error user received).
I'm a bit lost with debugging any further from here as the getConnection() method seems to be within compiled DLLs and not accessible by me.
What is the next step in trying to remove the error?

Firstly, it's unlikely that an SMTP password change has caused the issue from your description of it. But if that password change was made in the Web.config file, I'd say it's possible it was made less carefully than it should have been, and in fact a database connection-related section in there has been inadvertently modified and is no longer valid.
If you want to be able to debug into the DLL, you can disable the option to debug "Just My Code" in Visual Studio (something like Tools/Options/Debugging) - you should then be able to step down into these DLLs and see where the issue lies. Hopefully it won't require any code changes, and you can just fix up the configuration file.

Upgrade with SQL

I am converting a website over to ASP.NET 2.0, which supports .NET Framework versions 2.0 – 3.5. I am getting the following error message on a particular tab that is connected to a SQL DB. I am stuck at where this change needs to occur as I did not build this particular section of the site. Here is the error message and the Code. Any Help would be greatly appreciated.
Source Error:
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
Stack Trace:
[NullReferenceException: Object reference not set to an instance of an object.]
MagicAjax.AjaxCallHelper.GetPageHiddenDictionary(Page page, String fieldName) +37
MagicAjax.AjaxCallHelper.HandleClientScriptBlocks(Page page, Boolean
reflectToClient) +17
MagicAjax.AjaxCallHelper.Page_PreRender(Object sender, EventArgs e) +238
System.Web.UI.Control.OnPreRender(EventArgs e) +8996626
System.Web.UI.Control.PreRenderRecursiveInternal() +103
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean
includeStagesAfterAsyncPoint) +2496

.NET Unhandled Exception from MasterPage

I'm copying and pasting my application from one server (works fine) to another server (it doesn't work fine).
I get this on the new server, even though the code hasn't changed:
Source Error:
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
Stack Trace:
[NullReferenceException: Object reference not set to an instance of an object.]
MasterPagePS_Index.Page_Load(Object sender, EventArgs e) +117
System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
System.Web.UI.Control.OnLoad(EventArgs e) +99
System.Web.UI.Control.LoadRecursive() +50
System.Web.UI.Control.LoadRecursive() +141
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627

Are you accessing a database, file, or any external resources? Sounds like you have a configuration difference, check your web.config.

You don't use relative path in oder to access your ressource (File, page, style, assembly , etc...)
so ASP.Net don't find your file, throw null exception.

The error you provided doesn't give much information. I suggest that you perform a remote debugging and check which line is causing the error.
Or you can add the Global.asax file and catch the error in Application_Error and email the error to yourself.
Dim ex As Exception = Server.GetLastError()
Dim hue As System.Web.HttpUnhandledException = New System.Web.HttpUnhandledException(ex.Message, ex)
Dim html As String = hue.GetHtmlErrorMessage()
' TODO: Send the html string. This will send you the formatted html of the exception including the source of the error and stacktrace.

When I call Bitmap.Save function occur error "A generic error occurred in GDI+"

When I call Bitmap.Save function, this error occurs: "A generic error occurred in GDI+". When I call from localhost it work, but when I call from another computer this error occurs.
Server Error in '/jobnumber' Application:
A generic error occurred in GDI+.
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.Runtime.InteropServices.ExternalException: A generic error occurred in GDI+.
Source Error:
An unhandled exception was generated
during the execution of the current
web request. Information regarding the
origin and location of the exception
can be identified using the exception
stack trace below.
Stack Trace:
[ExternalException (0x80004005): A
generic error occurred in GDI+.]
System.Drawing.Image.Save(String
filename, ImageCodecInfo encoder,
EncoderParameters encoderParams)
+377518 System.Drawing.Image.Save(String
filename, ImageFormat format) +69
System.Drawing.Image.Save(String
filename) +25
Assignment.CreateBitmapImage(String
sImageText, Image Image1, JobInfo
job_info_param) +124
Assignment.PrintButton_Click(Object
sender, EventArgs e) +271
System.Web.UI.WebControls.Button.OnClick(EventArgs
e) +111
System.Web.UI.WebControls.Button.RaisePostBackEvent(String
eventArgument) +110
System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String
eventArgument) +10
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler
sourceControl, String eventArgument)
+13 System.Web.UI.Page.RaisePostBackEvent(NameValueCollection
postData) +36
System.Web.UI.Page.ProcessRequestMain(Boolean
includeStagesBeforeAsyncPoint, Boolean
includeStagesAfterAsyncPoint) +1565

This is usually an indication the web user (IIS_USR for example) has no rights to
save any data to the folder where you are saving the bitmap on the webserver.
I had similar problems before. Check the access rights on the server for that folder.
Start out by giving everyone full access to that folder (just to make sure that is the problem) then narrow it down again so only the required user has access.