C#•2mo ago

How to get rid of nullable warning?

What are the usual ways to get rid of these warnings? Do I have to check if everything is null before doing something? That would mean I would have to add a lot of if statements all the time which I hope could be prevented

7 Replies

Monsieur Wholesome•2mo ago

Do null checks and handle null cases Null coalescing operator Null conditional operator Null forgiving operator

Becquerel•2mo ago

you can either do null-checks or assert that the relevant variable/field is never null with annotations if the compiler knows something can never be null (it's given a value in a constructor), it won't give you these warnings

! 0Falco•2mo ago

So I have this code where I get data from an api which is nested in some objects I can retrieve it using: weatherData.Hourly.Time So this is a nested object but if I want the time value, I cannot just check if weatherData is null. I also have to check if weatherData.Hourly is null. But then my code ends up like this

if (weatherData != null) {
    if (weatherData.Hourly != null) {
        if (weatherData.Hourly.Time != null) { }
              }

if (weatherData != null) {
    if (weatherData.Hourly != null) {
        if (weatherData.Hourly.Time != null) { }
              }

Some nested if statements just to check if each object is not null I dont like that solution Any other options?

Monsieur Wholesome•2mo ago

if(weatherData?.Hourly?.Time is not null) // or "!= null"
{

}

if(weatherData?.Hourly?.Time is not null) // or "!= null"
{

}

if you are specifically wanting Time, you could also do

if(weatherData?.Hourly?.Time is { } time)
{
    // time is now a variable that was assigned from weatherData.Hourly.Time if none of them was null, and you can use it without typing it all out
}

if(weatherData?.Hourly?.Time is { } time)
{
    // time is now a variable that was assigned from weatherData.Hourly.Time if none of them was null, and you can use it without typing it all out
}

! 0Falco•2mo ago

class ApiManager
{
    public async Task<T?> ApiRequest<T>(string apiUrl, string apiKey = "")
    {
        using (var client = new HttpClient())
        {
            try
            {
                HttpResponseMessage response = await client.GetAsync(apiUrl);

                if (response.IsSuccessStatusCode)
                {
                    string responseBody = await response.Content.ReadAsStringAsync();

                    T model = JsonConvert.DeserializeObject<T>(responseBody);
                    return model;
                }
                else
                {
                    Console.WriteLine($"Failed to make request. Status code: {response.StatusCode}");
                    return default; // Return default value for type T
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine($"An error occurred: {ex.Message}");
                return default; // Return default value for type T
            }
        }
    }
}

class ApiManager
{
    public async Task<T?> ApiRequest<T>(string apiUrl, string apiKey = "")
    {
        using (var client = new HttpClient())
        {
            try
            {
                HttpResponseMessage response = await client.GetAsync(apiUrl);

                if (response.IsSuccessStatusCode)
                {
                    string responseBody = await response.Content.ReadAsStringAsync();

                    T model = JsonConvert.DeserializeObject<T>(responseBody);
                    return model;
                }
                else
                {
                    Console.WriteLine($"Failed to make request. Status code: {response.StatusCode}");
                    return default; // Return default value for type T
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine($"An error occurred: {ex.Message}");
                return default; // Return default value for type T
            }
        }
    }
}

I have the same issue for this line


T model = JsonConvert.DeserializeObject<T>(responseBody);

Using a if function to check if responsebody is null does not seem to work

leowest•2mo ago

Use System.Text.Json instead...

public async Task<T?> ApiRequest<T>(string apiUrl, string apiKey = "")
{
    try
    {
        return await client.GetFromJsonAsync<T>(apiUrl);
    }
    catch (Exception ex)
    {
        Console.WriteLine($"An error occurred: {ex.Message}");
        return default;
    }
}

public async Task<T?> ApiRequest<T>(string apiUrl, string apiKey = "")
{
    try
    {
        return await client.GetFromJsonAsync<T>(apiUrl);
    }
    catch (Exception ex)
    {
        Console.WriteLine($"An error occurred: {ex.Message}");
        return default;
    }
}

You may also consider using httpfactory instead to avoid exhaustion problems with using + httpclient

MODiX•2mo ago

https://learn.microsoft.com/en-us/aspnet/core/fundamentals/http-requests?view=aspnetcore-8.0 https://docs.microsoft.com/en-us/dotnet/standard/microservices-architecture/implement-resilient-applications/use-httpclientfactory-to-implement-resilient-http-requests

Make HTTP requests using IHttpClientFactory in ASP.NET Core

Learn about using the IHttpClientFactory interface to manage logical HttpClient instances in ASP.NET Core.

Use IHttpClientFactory to implement resilient HTTP requests - .NET

Learn how to use IHttpClientFactory, available since .NET Core 2.1, for creating HttpClient instances, making it easy for you to use it in your applications.

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How to get rid of nullable warning?