c# - Asserting with OR condition

Question

i am checking a string for three characters

Assert.AreEqual(myString.Substring(3,3), "DEF", "Failed as DEF  was not observed");

the thing is here it can be DEF or RES, now to handle this what i can think of is the following

bool check = false;
if( myString.Substring(3,3) == "DEF" || myString.Substring(3,3) == "RED" ) 
check = true;

Assert.IsTrue(check,"Failed");
Console.WriteLine(""Passed);

IS THERE a way i can use some OR thing within Assert

p.s i'm writing unit test & yes i will use ternary operator instead....

Answer 1

Assert.IsTrue((myString.Substring(3,3) == "DEF" || myString.Substring(3,3) == "RED")?true:false,"Failed");

Answer 2

Using NUnit, the AnyOf constraint works:

Assert.That(myString.Substring(3,3), Is.AnyOf("DEF", "RED"));