Is it possible in .Net to call some code only from debug builds of client assemblies?

public static class Ensures {
    public static Validation That {
        get { ... }
    }
}

public static class Requires {
    public static Validation That {
        get { ... }
    }
}

public static class Ensures {
    [ConditionalCallingCode("DEBUG")]
    public static Validation ThatDuringDebug {
        get { ... }
    }
}

public class Foo {
    public void Bar() {
        ... // do some work
        Ensures.That // do these checks always
            .IsNotNull(result)
            .IsInRange(result, 0, 100);

        Ensures.WhileDebuggingThat // only do these checks in debug mode
            .IsPositive(ExpensiveCalculation(result));

        return result;
    }
}

public class Foo {
    public void Bar() {
        ... // do some work
        Ensures.That // do these checks always
            .IsNotNull(result)
            .IsInRange(result, 0, 100);

        #ifdef DEBUG
        Ensures.That // only do these checks in debug mode
            .IsPositive(ExpensiveCalculation(result));
        #endif

        return result;
    }
}

using ValidationLibrary;
public static class EnsuresWhileDebugging {
    [Conditional("DEBUG")]
    public static Validation That() {
        return Ensures.That;
    }
}

Ensures.That.IsPositive(ExpensiveCalculation(result));

Ensures.WhileDebugging.That. IsPositive(() => ExpensiveCalculation(result));

try
{
     Debug.Assert(false);
}
catch (Exception e)
{
     // will only and always run in debug mode

}

Debug.Assert(!Properties.Settings.Default.UseAutoDebug);