blazor http generic client what is proper way to handle nulable type like this?

Question

I build some blazor app

and i want to have HttpGet like

person? x = await _httpClient.Get<person?>("url");

So from api if i return person then i want x to be it value, if from api i return NULL want to x be NULL

How to do this properly?

i have some httpclient with get like for example

public async Task<T> Get<T>(string uri, int timeOut = 100)
{           
        using var response = await _httpClient.SendAsync(new HttpRequestMessage(HttpMethod.Get, uri), linkedCts.Token);
        return await response.Content.ReadFromJsonAsync<T>();
    }
}

but the compilator on this response.Content.ReadFromJsonAsync<T>() says that possible null return

But still if I return NULL from api then it throws The input does not contain any JSON tokens. Expected the input to start with a valid JSON token, when isFinalBlock is true. Path: $ | LineNumber: 0 | BytePositionInLine: 0.'

so does i need it to change to be of Task<T?> so it may return null? what is right path here?

what is best approach for this ? or am I missing something and this is not right way ?

Thank You and regards!

Answer 1

In any call into a data pipeline - Server or API - you should consider returning a result object, not a T. This solves the problem of returning a null, you always return a result object, and you can include status information, such as success/failure and a failure message.

Here's what I use:

public sealed record ItemQueryResult<TRecord> : IDataResult
{
    public TRecord? Item { get; init;} 
    public bool Successful { get; init; }
    public string Message { get; init; } = string.Empty;

    private ItemQueryResult() { }

    public static ItemQueryResult<TRecord> Success(TRecord Item, string? message = null)
        => new ItemQueryResult<TRecord> { Successful=true, Item= Item, Message= message ?? string.Empty };

    public static ItemQueryResult<TRecord> Failure(string message)
        => new ItemQueryResult<TRecord> { Message = message};
}

For the record a list query result looks like this:

public sealed record ListQueryResult<TRecord> : IDataResult
{
    public IEnumerable<TRecord> Items { get; init;} = Enumerable.Empty<TRecord>();  
    public bool Successful { get; init; }
    public string Message { get; init; } = string.Empty;
    public long TotalCount { get; init; }

    private ListQueryResult() { }

    public static ListQueryResult<TRecord> Success(IEnumerable<TRecord> Items, long totalCount, string? message = null)
        => new ListQueryResult<TRecord> {Successful=true,  Items= Items, TotalCount = totalCount, Message= message ?? string.Empty };

    public static ListQueryResult<TRecord> Failure(string message)
        => new ListQueryResult<TRecord> { Message = message};
}

IDataResult provides a common interface for all results.

public interface IDataResult
{
    public bool Successful { get; }
    public string Message { get; }
}