Access QueryString, Route Parameter values in .net core webapi

Question

I have a unique situation where I need to get the DepartmentId from either the [FromRoute] or [FromQuery] or [FromBody]. This is weird as I cannot break my public api action contracts and cannot do much about it. Also I cannot alter the business contracts which is called inside from the controller, so that I cannot pass the DepartmentId down the pipeline.

I see that I can inject the IHttpContextAccessor and get the IHttpContextAccessor.HttpContext. I was able to get the DepartmentId for [FromQuery] as below:

request.QueryString.Value.Replace("?", "")
                            .Split("&")
                            .FirstOrDefault(x => x.Contains("departmentId"))
                            ?.Split("=")[1];

I am getting it [FromRoute] parameter as below;

var departmentId = 0;
var match = Regex.Match(request.Path, "Department/\\d+");
if (match.Success && match.Groups.Any())
{
    int.TryParse(match.Groups[0].Value.Replace("Department/", ""), out departmentId);
}

I do not know how I can get the DepartmentId from the [FromBody] complex object. But I do know that all the request objects used in the [HttpPost] is inheriting from the Department class which has a DepartmentId.

Any helps are appreciated....

Request.InputStream contains the body of the HTTP request; accessible as a Stream — CoolBots
– CoolBots, Commented May 10, 2018 at 19:02
I don't see the InputStream inside Request. I am using .net core if you have not noticed that. Did you mean IHttpContextAccessor.HttpContext.Request? — user007
– user007, Commented May 10, 2018 at 20:48
You could retrieve the DepartmentId from a middleware and then set a property of a scoped lifetime registered caching class. Then you wouldn't need to use HttpContextAccessor. As a side comment - using HttpContextAccessor carries performance costs, it's good to use other means to workaround it. — Simon Katanski
– Simon Katanski, Commented May 12, 2018 at 12:04

Simon Katanski · Accepted Answer · 2018-05-12 12:40:52Z

2

Using middleware I'd do something like this:

public class EstablishDepartmentMiddleware
{
    private RequestDelegate _next;

    public EstablishDepartmentMiddleware(RequestDelegate next)
    {
        this._next = next;            
    }

    public async Task InvokeAsync(HttpContext context, IDepartmentContext departmentContext)
    {            
        await TryGetDepartmentFromBody(context, departmentContext);
        // TryGetFromQuery
        // TryGetFromRoute
        await _next(context);
    }

    private static async Task TryGetDepartmentFromBody(HttpContext context, IDepartmentContext departmentContext)
    {
        using (var sr = new StreamReader(context.Request.Body))
        {
            var bodyText = await sr.ReadToEndAsync();
            var department = JsonConvert.DeserializeObject<Department>(bodyText);
            if (department != null)
            {
                departmentContext.DepartmentId = department.DepartmentId;
            }
        }
    }
}

Here are other classes:

public interface IDepartmentContext
{
    int DepartmentId { get; set; }
}

public class DepartmentContext : IDepartmentContext
{
    public int DepartmentId { get; set; }
}

public class Department
{
    public int DepartmentId { get; set; }
}

Here's what goes into the startup class:

app.UseMiddleware<EstablishDepartmentMiddleware>();

You can do something similar with action filters as well - middleware will work with all requests which arrive.

Obviously you can take the code above and using IHttpContextAccessor the same way get the DepartmentId from Body. Bear in mind - you might be leaking your infrastructure to your business layer - if you use the accessor in your business classes.

edited May 12, 2018 at 12:40

answered May 12, 2018 at 12:30

Simon Katanski

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3 Comments

user007 Over a year ago

Right now I am using the IHttpContextAccessor as I am tight on a deadline. But I will let my manager know about this one. Marking this as the answer for now. Thanks...

user007 Over a year ago

I got it working by following your instructions except in the post. The request Body becomes NULL after it is read. What can we do for that?

Simon Katanski Over a year ago

My bad - most probably it's because StreamReader is in a using() statement, which disposes the stream reader when it's getting out of scope. When SR disposes then the underlying stream is getting disposed as well. You can try removing the using statement and possibly also rewinding the stream as well.

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