`CallerArgumentExpression` is always null (C# 10)-CodePudding

I'm trying to use the CallerArgumentExpression attribute, in conjunction with the suggestion for validating records found here, but the expression is always null. I am doing this in a .NET6 Core console application. The exact same code works fine in LinqPad 7 (.NET6).

I have a base record that contains common validation methods (pretty much copied from that other answer)...

  public record CommonValidation {
    internal static bool NonEmptyOrNullString(string s, [CallerArgumentExpression("s")] string expr = default) {
      if (string.IsNullOrWhiteSpace(s)) {
        throw new ArgumentException($"{expr} cannot be null or empty");
      }
      return true;
    }

    internal static bool NonZeroInt(int n, [CallerArgumentExpression("n")] string expr = default) {
      if (n < 0) {
        throw new ArgumentException($"{expr} cannot be negative");
      }
      return true;
    }
  }

I can then create a record as follows...

  public record Address(string Street, string City, string State, string Country, string Postcode) : CommonValidation {
    private bool _ = NonEmptyOrNullString(Street)
                     && NonEmptyOrNullString(City)
                     && NonEmptyOrNullString(State)
                     && NonEmptyOrNullString(Country)
                     && NonEmptyOrNullString(Postcode);
  }

If I try to create an Address with an empty State...

Address a = new("5 My Street", "Somewhere", "", "Oz", "12345");

...then the exception is thrown, but the expr variable is null. As I said, the exact same code works fine in LinqPad, even though both are using the same version of .NET/C#.

Anyone able to explain what's going wrong in the console app? Thanks

CodePudding user response：

Visual Studio 2019 doesn't support C# 10. Make sure you're using Visual Studio 2022. LinqPad 7 does which is why it works there.