Why can't I post from my Xamarin Frorms app to my .net core web api

问题

I have a post method that sends json to my api.

My endpoint works in postman so my problem is in my xamarin post request:

    async void RegisterUser(object sender, System.EventArgs e)
    {
        string URL = "http://blablahblah:51001/register";

        HttpClient client = new HttpClient();

        var model = new RegisterViewModel
        {
            Email = EntryEmail.Text,
            FirstName = FirstName.Text,
            LastName = LastName.Text, 
            Password = EntryPasswrd.Text 

        };

        var content = JsonConvert.SerializeObject(model);

        await client.PostAsync(URL, new StringContent(content));

    }

after it hits the await client.PostAsync(URL, new StringContent(content)); line, the application just stops dead. no error messages or anything like that.

Any ideas?

EDIT:

My register method in my API solution:

    [Route("register")]
    [HttpPost]
    public async Task<ActionResult> InsertUser([FromBody] RegisterViewModel model)
    {
        var user = new IdentityUser
        {
            Email = model.Email,
            UserName = model.Email,
            SecurityStamp = Guid.NewGuid().ToString()
        };

        var result = await _userManager.CreateAsync(user, model.Password);
        if (result.Succeeded)
        {
            var newUser = new User
            {
                Username = model.Email,
                FirstName = model.FirstName,
                LastName = model.LastName
            };

            _dbContext.Users.Add(newUser);
            await _dbContext.SaveChangesAsync();

        }
        return Ok(new { Username = user.UserName });
    }

and my view model i am passing the data through:

public class RegisterViewModel
{
    [Required]
    [EmailAddress]
    public string Email { get; set; }

    [Required]
    public string FirstName { get; set; }

    [Required]
    public string LastName { get; set; }

    [Required]
    public string Password { get; set; }
}

I have since rewrote my post method using the below suggestions, its still not returning any errors inside my catch block:

    public async Task<string> Registered(object details)
    {
        string URL = "http://blahblah:51001/register";

        HttpClient client = new HttpClient();

        var model = new RegisterViewModel
        {
            Email = EntryEmail.Text,
            FirstName = FirstName.Text,
            LastName = LastName.Text,
            Password = EntryPasswrd.Text

        };

        var content = JsonConvert.SerializeObject(model);

        try
        {
            await client.PostAsync(URL, new StringContent(content));
        }
        catch (Exception ex)
        {

            throw new Exception(ex.Message);
        }


        return "Registration Successful";
    }

回答1:

Please test the Web Api with some REST testing tool like POSTMAN, to verify that it works with your JSON data firstly.

If your webapi have no problems, please take a look the following code, I can post data to asp.net core webapi successfully, and return value.

 private async void btnpost_Clicked(object sender, EventArgs e)
    {
        ContactModel cm = new ContactModel() {ID=1,Name="cherry",Age=12 };

        var httpClient = new HttpClient();
        var content = JsonConvert.SerializeObject(cm);
        HttpContent httpContent = new StringContent(content, Encoding.UTF8);
        httpContent.Headers.ContentType = new MediaTypeHeaderValue("application/json");
        var uri = new Uri("http://xxx.xx.xx.xx:8088/api/Contact");
        HttpResponseMessage response = await httpClient.PostAsync(uri, httpContent);
        if (response.IsSuccessStatusCode)
        {
            var data = await response.Content.ReadAsStringAsync();

            string ss = data;
        }

    }

Please note: Adding android:usesCleartextTraffic="true" in Mainfeast.xml,because starting with Android 9 (API level 28), cleartext support is disabled by default. if not, you may have Cleartext HTTP traffic not permitted error.

回答2:

So after 2 days of googling i found a solution:

https://marketplace.visualstudio.com/items?itemName=vs-publisher-1448185.ConveyorbyKeyoti#overview

now I can post to my api from my xamarin forms project!!!

thanks for everyone's input

来源：https://stackoverflow.com/questions/62143179/why-cant-i-post-from-my-xamarin-frorms-app-to-my-net-core-web-api