C# win form sending a message on telegram to a pr. channel exception error

Question

C# win form sending a message on telegram to a pr. channel exception error

Gennady Gurin 251

Sending a message to a private channel on Telegram,

not sure why I get exception message when running code.

I attached 2 files.

https://1drv.ms/i/c/4bb745d09a980e0c/IQAgTbHfYIUFR7SS9C1J1elwAcWxLDv1-fFFqxvo8SM3YXo?e=EFa1FV

https://1drv.ms/i/c/4bb745d09a980e0c/IQBkO7GluIWcQYgtIXCHiKQgAYTIu7Li8xnhoJV0brKMwFU?e=N6o6TS

Anyone knows,

Thanks in advance.

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Answer 1

Brian Pham (WICLOUD CORPORATION) 1,340 Microsoft External Staff Moderator

Hi Gennady Gurin ,

Thank you for sharing the complete error message.

The failure occurs before the request reaches Telegram. The runtime is attempting to load: System.Text.Json, Version=8.0.0.0 but the System.Text.Json assembly available at runtime likely does not match the assembly identity expected by Telegram.Bot or one of its dependencies.

Please try the following:

Check the project’s <TargetFramework> or <TargetFrameworkVersion> value.
In Visual Studio, restore the NuGet packages, clean the solution, and rebuild it
If the issue persists, close Visual Studio and remove the project's bin and obj folders before rebuilding
In Manage NuGet Packages for Solution > Consolidate, align the Telegram.Bot and System.Text.Json versions across all projects.
Check for manually added references to System.Text.Json.dll and verify that they are consistent with the NuGet package configuration.
Restore the NuGet packages and rebuild the solution.

After rebuilding, check the DLL’s assembly identity by updating and running this command for example:

[System.Reflection.AssemblyName]::GetAssemblyName( "C:\Path\To\Application\bin\Debug\System.Text.Json.dll" ).FullName

Compare the result with:

System.Text.Json, Version=8.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51

If the project targets .NET Framework, also add the following to the .csproj file:

<PropertyGroup>
	  <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
</PropertyGroup>

If the project targets .NET 6 or later, do not add a .NET Framework binding redirect. If the issue persists, please replace ex.Message with ex.ToString() and provide:

The project’s target framework
The Telegram.Bot version
The System.Text.Json package version
The PowerShell command output
The complete exception output by change ex.Message to ex.ToString()

Please remove any sensitive information, including your bot token, before sharing code or logs.

If you found my response helpful or informative, I would greatly appreciate it if you could follow this guide for your confirmation. Thank you.

Gennady Gurin 251 Reputation points

2026-10-23T02:42:12.1833333+00:00

hi, I will try, but this might take take since I probably have not done such configurations in a past,

anyway, my project targets old .NET framework 4.8, but I think this bot is meant for newer version(s),

but I am not sure.

Get back, thanks. These are very helpful, waiting for response.
Brian Pham (WICLOUD CORPORATION) 1,340 Reputation points Microsoft External Staff Moderator

2026-10-23T03:22:44.3433333+00:00
Hi @Gennady Gurin ,

Thank you for confirming that the project targets .NET Framework 4.8. That information is helpful and narrows down the troubleshooting path.

Telegram.Bot is not necessarily limited to newer .NET versions. A .NET Framework 4.8 project can use a package version that provides a compatible .NET Standard 2.0 assembly. However, compatibility depends on the exact version of Telegram.Bot installed, so please check it as follows:

In Visual Studio, right-click the project and select Manage NuGet Packages.

Open the Installed tab.

Locate Telegram.Bot and note its installed version.

Check the package’s supported target frameworks on its NuGet package page.

NuGet selects the most appropriate compatible framework asset available in a package. You can find additional information in Microsoft’s documentation on NuGet package compatibility.

Because the project builds and reaches the SendMessage call, the current exception appears more consistent with a runtime assembly-loading conflict involving System.Text.Json than with Telegram.Bot being entirely incompatible with .NET Framework 4.8.

Please take your time working through the troubleshooting steps in my previous response. Once you have tried them, please share the installed Telegram.Bot version and the results here.

If you encounter any difficulties or have questions along the way, feel free to ask. I'll be happy to help you work through them.
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Gennady Gurin 251 Reputation points

2026-10-23T03:52:52.15+00:00

twenty two-ten-three-three latest version installed, but which do i need?
Brian Pham (WICLOUD CORPORATION) 1,340 Reputation points Microsoft External Staff Moderator

2026-10-23T04:14:49.3566667+00:00

Hi @Gennady Gurin ,

Thank you for confirming the package version.

I checked the NuGet page for Telegram.Bot 22.10.3, and this version supports .NET Standard 2.0, which is compatible with your .NET Framework 4.8 project. Therefore, you do not need to downgrade Telegram.Bot or upgrade your entire application solely because of the target framework.

Have you had a chance to try the troubleshooting steps from my previous response? If so, please let me know the results and whether the issue persists.
Gennady Gurin 251 Reputation points

2026-10-23T15:51:51.79+00:00

Probably over the weekend, I will trouble shoot, I will let you know.

Best regards.
Gennady Gurin 251 Reputation points

2026-10-25T01:19:15.7+00:00

hi, I add lines into XML .csproj file and changed to ex.ToString() I got this error:

How to find out The System.Text.Json package version?

Let me know next step, thanks.
Brian Pham (WICLOUD CORPORATION) 1,340 Reputation points Microsoft External Staff Moderator

2026-10-26T02:32:56.68+00:00
Hi @Gennady Gurin ,

Thank you for updating the project file and providing the complete output from ex.ToString().

To check the NuGet package version, open Manage NuGet Packages > Installed, search for System.Text.Json, and share the displayed version.

If it is not listed, run the following in Tools > NuGet Package Manager > Package Manager Console:

Get-Package -ProjectName "WindowsFormsApplication-Test3" | Where-Object { $_.Id -eq "System.Text.Json" }

If neither method shows the package, please let me know. It may be included indirectly as a dependency of Telegram.Bot.

I understand that you have already added the automatic binding redirect setting to the .csproj file. Could you also confirm whether you completed the remaining steps from my first response?

Closed all instances of Visual Studio.

Deleted the project’s bin and obj folders.

Restored the NuGet packages and rebuilt the solution.

Checked that System.Text.Json.dll was not also added manually through Add Reference > Browse.

Once you provide the installed System.Text.Json package version, the next step will depend on the result:

If no package is installed directly, we will check whether it is included indirectly by Telegram.Bot.

If an 8.0.x package is installed, reinstalling the same version and performing a clean rebuild may replace a stale or inconsistent DLL.

If a 7.x or earlier package is installed, it may need to be updated to a compatible 8.0.x version.
Gennady Gurin 251 Reputation points

2026-10-27T03:23:00.16+00:00

System.Text.Json version 8.0.5 installed.
Gennady Gurin 251 Reputation points

2026-10-27T03:23:29.41+00:00

System.Text.Json version 8.0.5 installed.

You meant first I have to delete bin and obj folders then reinstall all NuGet packages?

How to "Restored the NuGet packages"?

You mean I have to install all NuGet packages again? I have several to install.

Let me know...
Brian Pham (WICLOUD CORPORATION) 1,340 Reputation points Microsoft External Staff Moderator

2026-10-27T03:47:30.8233333+00:00
Hi @Gennady Gurin ,

Thank you for confirming that System.Text.Json 8.0.5 is installed.

You do not need to reinstall all NuGet packages manually. Restore NuGet Packages instructs Visual Studio to read the existing package references from the project and automatically download any packages that are missing.

Since System.Text.Json 8.0.5 is already installed, the next step is to reinstall only that package. This may replace a stale or inconsistent DLL or repair its project reference.

Please open:

Tools > NuGet Package Manager > Package Manager Console

Then run:

Update-Package System.Text.Json -ProjectName "WindowsFormsApplication-Test3" -Reinstall

This command reinstalls only System.Text.Json and its applicable dependencies for the specified project. It does not require you to manually reinstall every NuGet package.

After the command completes:

In Solution Explorer, right-click the project and select Open Folder in File Explorer.

Close all instances of Visual Studio.

Delete only the bin and obj folders in the project folder. These folders contain generated build files and will be recreated automatically. Do not delete the .csproj file or any source-code files.

Reopen the solution in Visual Studio.

In Solution Explorer, right-click the solution and select Restore NuGet Packages.

Wait for the restore operation to finish and check the Output window for any errors.

Select Build > Clean Solution.

Select Build > Rebuild Solution.

Run the application again and check whether the same exception occurs.

Please let me know whether the reinstall command completes successfully and whether the same exception appears after rebuilding.

Thank you.
Gennady Gurin 251 Reputation points

2026-10-27T19:31:18.38+00:00

Output after Restore NuGet Packages:

I got another error:

also the warnings, but that is another issues:

Processing COM reference "WMPLib" from path "C:\WINDOWS\system32\wmp.dll". At least one of the arguments for 'IWMPGraphEventHandler.NotifyAcquireCredentials' cannot be marshaled by the runtime marshaler. Such arguments will therefore be passed as a pointer and may require unsafe code to manipulate.

The referenced component 'Microsoft.Extensions.DependencyInjection.Abstractions' could not be found.

Processing COM reference "WMPLib" from path "C:\WINDOWS\system32\wmp.dll". Type library importer encountered a property getter 'sessionPlaylistCount' on type 'WMPLib.IWMPNowPlayingHelperDispatch' without a valid return type. The importer will attempt to import this property as a method instead.

The referenced component 'WindowsFormsApplication-Test3.vshost.exe.manifest' could not be found.

Could not resolve reference "MyApplication.app, Version=1.0.0.0". If this reference is required by your code, you may get compilation errors.
Brian Pham (WICLOUD CORPORATION) 1,340 Reputation points Microsoft External Staff Moderator

2026-10-28T03:51:04.8666667+00:00
Hi @Gennady Gurin ,

Thank you for sharing the latest result.

Based on the new exception, the previous System.Text.Json assembly mismatch no longer appears. The application is now able to reach the Telegram Bot API.

Could you please confirm that you no longer receive the following error?

And as I can see you have a new error:

Telegram Bot API error 400: Bad Request: chat not found

This is a separate issue from the original System.Text.Json dependency problem. It indicates that Telegram cannot find or access the chat specified by the current chatId.

Please briefly verify that:

The chatId is the actual ID of the target channel.

The bot associated with the token has been added to that channel.

The bot has permission to post messages in the channel.

The bot token belongs to the same bot that was added to the channel.

An invitation link is not being used as the chatId.

For a public channel, you can use its username in this format: chatId: "@channel_username"

For a private channel, the correct numeric channel ID is required.

The build warnings shown in the screenshot appear to be separate from both the resolved System.Text.Json issue and the new Telegram API response. Please first confirm whether the original System.Text.Json error has been resolved.

If you found my response helpful or informative, I would greatly appreciate it if you could follow this guide for your confirmation. Thank you.
Gennady Gurin 251 Reputation points

2026-10-28T21:48:22.5466667+00:00

I confirm that the original System.Text.Json error has been resolved.

It is a private channel, just added bot to my private channel and it worked I received a message!

Thanks, I actually have another program issue, I might have to make another post.

I will mark this as an answer. Will be in touch. All the best.