Hi Andy-8783,
>>If I can see a Component in .Net 5 toolbox like an ErrorProvider,
You can find the ErrorProvider under Toolbox->Components tab.
And as lextm said that the WinForms designer in .NET Core is still in its preview and currently some features are not yet supported.
I suggest you use the “Send Feedback” icon in Visual Studio top-right corner as shown in the following image and specify that it is related to the “WinForms .NET Core” area.
More details please refer to this document.
Best Regards,
Daniel Zhang
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