Casting a C# Object From Its Parent

Have you ever tried to do something akin to the following?

[Fact]
public void ConvertClassToSubClass_Converts()
{
    // Arrange
    var parentClass = new SimpleTestClass();
    parentClass.Property1 = "test";

    // Act
    var childClass = parentClass as SimpleTestSubClass;

    // Assert
    Assert.Equal("test", childClass.Property1);
}

This is a simple Xunit (failing) test. The reason it fails is because you (or I) am trying to cast a general type to a specific, and C# is complaining that this may not be possible; consequently, you will get null (or for a hard cast, you’ll get an InvalidCastException).