I am getting an error when trying to open my Winform in design view

Quatic 1

I am getting the follow error when trying to open my winform in design view in visual studio 2022 (C#)

System.UriFormatException: Invalid URI: The hostname could not be parsed.
at System.Uri.CreateThis(String uri, Boolean dontEscape, UriKind uriKind, UriCreationOptions& creationOptions)
at System.Uri..ctor(String uriString)
at System.Configuration.ClientConfigPaths..ctor(String exePath, Boolean includeUserConfig)
at System.Configuration.ClientConfigPaths.GetPaths(String exePath, Boolean includeUserConfig)
at System.Configuration.ClientConfigurationHost.get_ConfigPaths()
at System.Configuration.ClientConfigurationHost.GetStreamName(String configPath)
at System.Configuration.ClientConfigurationHost.get_IsAppConfigHttp()
at System.Configuration.Internal.DelegatingConfigHost.get_IsAppConfigHttp()
at System.Configuration.ClientConfigurationSystem..ctor()
at System.Configuration.ConfigurationManager.EnsureConfigurationSystem()

Jack J Jun 24,311 Reputation points Microsoft Vendor

2022-02-03T08:16:47.143+00:00

@Quatic , what do have done caused the problem? Could you provide some pictures or some code with me so that I can reproduce your problem?
Quatic 1 Reputation point

2022-02-09T15:33:35.63+00:00

It started when I implemented a base form (abstract class) but not immediately but some time after I implemented it. My guess is that something “designer generated” is causing the problem. I don’t have extensive knowledge on what the design view does/how it is generated so that’s where my knowledge stops. I can post code later.
Saga 426 Reputation points

2022-02-10T22:07:34.163+00:00

Hi, there is a possibility that the designer.cs code file that corresponds to your form was modified in such a way that the IDE did not like.

This has happened to me. One way to fix it is to remove whatever changes you made and restore the form to how it was before you started getting this error.

Another way to fix this is op open the designer.cs file and look inside to see if something does not look right. I should mention that this is not easy because it is hard to tell where the problem is. One possible way is to run the program and let it error out, then in the error list, have a look where the error is being generated.

One item caught my attention from the message text that you posted:

at System.Uri..ctor(String uriString)

Why the two dots? And what is ctor?

Is there a chance that these lines should be different?

Saga
Quatic 1 Reputation point

2022-02-11T14:13:37.767+00:00

The code is at design timewhen I try to open the designer, so all that code is by Microsoft (I figured) however, the double .. you've spotted has me questioning, nicely spotted! It would not be the first time that a typo costs me hours of testing and searching. ctor stands for constructor. So I actually think the .. is correct and just a way of MS to say its a constructor being called and not a method called ctor. The designer changing things a round making the thning not work sounds familiar ;). I'll look around the code a bit again to see whats different. I also use Git so I can compare historical versions. Will let you know the outcome.
Karen Payne MVP 35,201 Reputation points

2022-02-11T15:11:05.147+00:00

As I see it, use abstract will causes issues.

The designer has to be able to initialize an object of that type, and it can't initialize an abstract class.

1 answer

Quatic 1 Reputation point

2022-02-11T22:24:57.837+00:00

So I caught the culprit for this little nasty bug, this was in the designer generated code:

this.Load += new System.EventHandler(this.listBase_Load);
and for some reason this listBase_Load was an async function causing the whole thing to crash. Fix was to not make the load event call an async function.
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I am getting an error when trying to open my Winform in design view

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