SetUpAllProperties does not provide stubbing behavior for virtual properties.

[apeneve]

I have a simple public virtual string Foo {get;set;} on my class to be mocked.
The mocked object does not remember the value I pass in via mock.Object.Foo = "bar"; even after i call mock.SetUpAllProperties().

As far as I can tell this used to work in an older version. Isn't "stubbing" or "property behavior" supposed to work with virtual properties?

[stakx]

Do you mean something like the following?

[Fact]
public static void MockRemembersPropertyValue()
{
    var mock = new Mock<C>();
    mock.SetupAllProperties();
    mock.Object.Foo = "bar";
    Assert.Equal("bar", mock.Object.Foo);
}

public class C
{
    public virtual string Foo { get; set; }
}

This test passes in the current version of Moq (4.7.49).

If I misunderstood your scenario, please report back with a small but complete repro code and an indication of which version of Moq you're using. In the meantime, I am closing this issue as "non-reproducible error".