Can I use a field on my test class as a parameter to an XUnit Theory?

I like to define named test data as fields on my test class, and sometimes multiple are run against the same test using a Theory.
I've used MemberData but this appears to only support IEnumerable so I have to write somewhat ugly wrapper enumerables:

public class MyTests
{
	public static string s1 = "test";
	public static string s2 = "bees";
	public static string s3 = "pear";
	public static string s4 = "joke";

	public static IEnumerable<object[]> Strings => new List<object[]>
	{
		new object[] { s1 },
		new object[] { s2 },
		new object[] { s3 },
		new object[] { s4 },
	};

	[Theory]
	[MemberData(nameof(Strings))]
	public void ContainsLetterE(string s)
	{
		s.Should().Contain("e");
	}
}

What I am wondering is if there is a way to use explicit fields/properties, along the lines of:

public class MyTests
{
	public static string s1 = "test";
	public static string s2 = "bees";
	public static string s3 = "pear";
	public static string s4 = "joke";

	[Theory]
	[Field(nameof(s1))]
	[Field(nameof(s2))]
	[Field(nameof(s3))]
	[Field(nameof(s4))]
	public void ContainsLetterE(string s)
	{
		s.Should().Contain("e");
	}
}

Is this possible at all, or does it have to be IEnumerable based?

Writing it as answer since it's quite big.

>InlineDataAttribute means I have to re-type the same in several places which increases risk of error.

if you define this as constants then you can provide these constants itself instead of typing values.

if you don't want doing it, then you have a huge number of xunit customization approaches that will require some work though.

1. You can define your own attribute inherited from DataAttribute (See example here).

   public override IEnumerable<object[]> GetData(MethodInfo testMethod)
   ...
   

Then if you add this attribute to your test, in MethodInfo testMethod you will have full information about test itself, base class and so on, including applied custom attributes. One workflow example that you can consider is using this new data attribute (for a test itself) with a different custom attribute like ValuesAttribute similar to:

[AttributeUsage(AttributeTargets.Parameter)]
public sealed class ValuesAttribute : Attribute
{
    private readonly object[] _values;

    public ValuesAttribute(params object[] values)
    {
        _values = values;
    }

    public object[] GenerateValues()
    {
        return _values;
    }
}

which will allow you reading custom input for a test and generate test cases in flight. If I understand what you're asking correctly it will be:

[Theory]
[CustomDataAttribute]
public void Test(Values(nameof(s1), nameof(s2)) OutputType value)
...

where inside CustomDataAttribute you will need to read ValuesAttribute value from parameter via reflection, then read fields you need from the test class itself with reflection too and eventually properly fill output here public override IEnumerable<object[]> as OutputType.

2. Implement your own logic for MemberData like below. Note: it's simplified above approach since MemberDataAttributeBase is inherited from DataAttribute

   public class CustomMemberData : MemberDataAttributeBase
   {
      public CustomMemberData(string memberName, object[] parameters) : base(memberName, parameters)
      {
      }
   
      protected override object[] ConvertDataItem(MethodInfo testMethod, object item) => /*your logic*/;
   }
   

There are more ways, but the idea is that you can customize almost everything in xunit workflow if you need to But you need to write some infrustructure for it.