KeyConverter does not throw NotSupportedException on undefined values

[h3xds1nz]

Description

KeyConverter, unlike ModifierKeysConverter and MouseActionConverter for example, does not throw NotSupportedException but throws ArgumentException instead due to the usage of Enum.Parse instead of Enum.TryParse.

This results in a dead-code being present with proper exception (key can never be null):

wpf/src/Microsoft.DotNet.Wpf/src/WindowsBase/System/Windows/Input/KeyConverter.cs

Lines 89 to 97 in cc07628

	object key = GetKey(fullName, CultureInfo.InvariantCulture);
	if (key != null)
	{
	return ((Key)key);
	}
	else
	{
	throw new NotSupportedException(SR.Format(SR.Unsupported_Key, fullName));
	}

It is also the exception that is documented:
https://learn.microsoft.com/en-us/dotnet/api/system.windows.input.keyconverter.convertfrom

Reproduction Steps

Create KeyConverter instance, try to from string with a key that is not defined in the enum, e.g. "MyAmazingKey".

Expected behavior

We will receive NotSupportedException with SR.Unsupported_Key message.

Actual behavior

We receive ArgumentException originating from Enum.Parse.

Regression?

Nope, has been the case since NetFX but it is inconsistent and undocumented.

Impact

Unexpected exception for TypeConverter is thrown.

Next Steps

I plan to submit a PR fixing this behavior, simply by using TryParse instead for the fallback.

[miloush]

I tried to find some code that would break but didn't have much luck so far. Most people don't catch exceptions here, a few catch all exceptions.

[hongruiyu]

I tested it in WPF with the following code, and indeed an incorrect error occurred.

public void Fun()
{
    KeyConverter keyConverter = new KeyConverter();
    ITypeDescriptorContext context = null; 
    CultureInfo culture = CultureInfo.InvariantCulture;
    string keyString = "Ente"; //Incorrect keyString
    //string keyString = "Enter";   //Correct keyString

    try
    {
        Key key = (Key)keyConverter.ConvertFrom(context, culture, keyString);
        MessageBox.Show($"Converted key: {key}");
    }
    catch (NotSupportedException ex)
    {
        MessageBox.Show($"NotSupportedException: {ex.Message}");
    }
    catch (ArgumentException ex)
    {
        MessageBox.Show($"ArgumentException: {ex.Message}");
    }
    catch (Exception ex) 
    {
        MessageBox.Show($"Other Errors: {ex.Message}");
    }
}