Suppress Compiler "null check" Warning Conditionally-CodePudding

I have a centralized method for checking results from a repository. This includes a check if the Entityproperty is null.

Sadly this has the annoying side-effect of showing a compiler warning, since there is no null check in the method that contains the call.

This is probably a long shot, but is there a way to tell the compiler to treat my method like a manual null check? I would prefer not to disable the warning globally, since it is actually pretty useful. Are there any other workarounds for this?

public Group GetGroup(Group.GroupId groupId)
{
    if (groupId.Value == null || groupId.Is(0))
        throw new Exception("Can not get group with ID: null/0");

    EntityInteractionResult<Group> readResult = _groupRepository.ReadById((ulong)groupId.Value);

    readResult.ValidateSuccessAndEntity(); // <- This checks if Entity is null
    return readResult.Entity; // <- CS8603 possible null reference return
}

CodePudding user response：

If ValidateSuccessAndEntity is method of EntityInteractionResult then you can use MemberNotNullAttribute to list members which won't be null when the method returns:

public class Result
{
    public string? Value { get; set; } 

    public Result()
    {
    }

    [MemberNotNull(nameof(Value))]
    public void Validate()
    {
        if(Value is null)
            throw new Exception();
    }
}

var result = new Result();
result.Validate();
var c = result.Value[1]; // "warning CS8602: Dereference of a possibly null reference" if previous line commented out

Demo

Attributes for null-state static analysis interpreted by the C# compiler