Answer by Arjun for ASP.NET Core Web API exception handling

Well accepted answer helped me a lot but i wanted to pass HttpStatusCode in my middleware to manage error status code at runtime.

According to this link i got some idea to do the same. So i merged the Andrei Answer with this. So my final code is below:
1. Base class

public class ErrorDetails
{
    public int StatusCode { get; set; }
    public string Message { get; set; }

    public override string ToString()
    {
        return JsonConvert.SerializeObject(this);
    }
}

2. Custom Exception Class Type

 public class HttpStatusCodeException : Exception
{
    public HttpStatusCode StatusCode { get; set; }
    public string ContentType { get; set; } = @"text/plain";

    public HttpStatusCodeException(HttpStatusCode statusCode)
    {
        this.StatusCode = statusCode;
    }

    public HttpStatusCodeException(HttpStatusCode statusCode, string message) : base(message)
    {
        this.StatusCode = statusCode;
    }

    public HttpStatusCodeException(HttpStatusCode statusCode, Exception inner) : this(statusCode, inner.ToString()) { }

    public HttpStatusCodeException(HttpStatusCode statusCode, JObject errorObject) : this(statusCode, errorObject.ToString())
    {
        this.ContentType = @"application/json";
    }

}

3. Custom Exception Middleware

public class CustomExceptionMiddleware
    {
        private readonly RequestDelegate next;

    public CustomExceptionMiddleware(RequestDelegate next)
    {
        this.next = next;
    }

    public async Task Invoke(HttpContext context /* other dependencies */)
    {
        try
        {
            await next(context);
        }
        catch (HttpStatusCodeException ex)
        {
            await HandleExceptionAsync(context, ex);
        }
        catch (Exception exceptionObj)
        {
            await HandleExceptionAsync(context, exceptionObj);
        }
    }

    private Task HandleExceptionAsync(HttpContext context, HttpStatusCodeException exception)
    {
        string result = null;
        context.Response.ContentType = "application/json";
        if (exception is HttpStatusCodeException)
        {
            result = new ErrorDetails() { Message = exception.Message, StatusCode = (int)exception.StatusCode }.ToString();
            context.Response.StatusCode = (int)exception.StatusCode;
        }
        else
        {
            result = new ErrorDetails() { Message = "Runtime Error", StatusCode = (int)HttpStatusCode.BadRequest }.ToString();
            context.Response.StatusCode = (int)HttpStatusCode.BadRequest;
        }
        return context.Response.WriteAsync(result);
    }

    private Task HandleExceptionAsync(HttpContext context, Exception exception)
    {
        string result = new ErrorDetails() { Message = exception.Message, StatusCode = (int)HttpStatusCode.InternalServerError }.ToString();
        context.Response.StatusCode = (int)HttpStatusCode.BadRequest;
        return context.Response.WriteAsync(result);
    }
}

4. Extension Method

public static void ConfigureCustomExceptionMiddleware(this IApplicationBuilder app)
    {
        app.UseMiddleware<CustomExceptionMiddleware>();
    }

5. Configure Method in startup.cs

app.ConfigureCustomExceptionMiddleware();
app.UseMvc();

Now my login method in Account controller :

 try
        {
            IRepository<UserMaster> obj = new Repository<UserMaster>(_objHeaderCapture, Constants.Tables.UserMaster);
            var Result = obj.Get().AsQueryable().Where(sb => sb.EmailId.ToLower() == objData.UserName.ToLower() && sb.Password == objData.Password.ToEncrypt() && sb.Status == (int)StatusType.Active).FirstOrDefault();
            if (Result != null)//User Found
                return Result;
            else// Not Found
                throw new HttpStatusCodeException(HttpStatusCode.NotFound, "Please check username or password");
        }
        catch (Exception ex)
        {
            throw ex;
        }

Above you can see if i have not found the user then raising the HttpStatusCodeException in which i have passed HttpStatusCode.NotFound status and a custom message
In middleware

catch (HttpStatusCodeException ex)

blocked will be called which will pass control to

private Task HandleExceptionAsync(HttpContext context, HttpStatusCodeException exception) method

.


But what if i got runtime error before? For that i have used try catch block which throw exception and will be catched in catch (Exception exceptionObj) block and will pass control to

Task HandleExceptionAsync(HttpContext context, Exception exception)

method.

I have used a single ErrorDetails class for uniformity.