An ApiController parameter is receiving a null value for a complex type

Question

An ApiController parameter is receiving a null value for a complex type

For some reason, the parameter "ParametroFiltro Filtro" is returning null in my code, while the other parameters ("page" and "pageSize") are working correctly.

public class ParametroFiltro
{
    public string Codigo { get; set; }
    public string Descricao { get; set; }
}

This is my ApiController's Get method:

public PagedDataModel<ParametroDTO> Get(ParametroFiltro Filtro, int page, int pageSize)

Below is my ajax call:

var fullUrl = "/api/" + self.Api;
$.ajax({
    url: fullUrl,
    type: 'GET',
    dataType: 'json',
    data: { Filtro: { Codigo: '_1', Descricao: 'TESTE' }, page: 1, pageSize: 10 },
    success: function (result) {
        alert(result.Data.length);
        self.Parametros(result.Data);
    }
});

c#ajax json asp.net-web-api

Answer 1

Answer №1

If you are attempting to send a complex object using the GET method, it will fail because GET does not support a request body and instead encodes all values into the URL. To resolve this issue, you can utilize the [FromUri] attribute, but first, you must update your client-side code:

$.ajax({
    url: fullUrl,
    type: 'GET',
    dataType: 'json',
    data: { Codigo: '_1', Descricao: 'TESTE', page: 1, pageSize: 10 },
    success: function (result) {
        alert(result.Data.length);
        self.Parametros(result.Data);
    }
});

By making this adjustment, [FromUri] will be able to extract properties from your complex object directly from the URL if you modify your action method as follows:

public PagedDataModel<ParametroDTO> Get([FromUri]ParametroFiltro Filtro, int page, int pageSize)

An alternative approach would be to use the POST method, which supports a request body (in this case, you would need to use JSON.stringify() to format the body as JSON).

Answer 2

If you are attempting to send a complex object using the GET method, it will fail because GET does not support a request body and instead encodes all values into the URL. To resolve this issue, you can utilize the [FromUri] attribute, but first, you must update your client-side code:

$.ajax({
    url: fullUrl,
    type: 'GET',
    dataType: 'json',
    data: { Codigo: '_1', Descricao: 'TESTE', page: 1, pageSize: 10 },
    success: function (result) {
        alert(result.Data.length);
        self.Parametros(result.Data);
    }
});

By making this adjustment, [FromUri] will be able to extract properties from your complex object directly from the URL if you modify your action method as follows:

public PagedDataModel<ParametroDTO> Get([FromUri]ParametroFiltro Filtro, int page, int pageSize)

An alternative approach would be to use the POST method, which supports a request body (in this case, you would need to use JSON.stringify() to format the body as JSON).

Answer 3

Answer №2

Remember to include the contentType property in your ajax call, and utilize the JSON.stringify method to construct the JSON data for posting. Make sure to set the type as POST, allowing MVC Model binding to automatically bind the posted data to your class object.

var filter = { "Filtro": { "Codigo": "_1", "Descricao": "TESTE" }, 
                                               "page": "1", "pageSize": "10" }; 
$.ajax({
    url: fullUrl,
    type: 'POST',
    dataType: 'json',
    contentType: 'application/json',
    data: JSON.stringify(filter),
    success: function (result) {
        alert(result.Data.length);
        self.Parametros(result.Data);
    }
});

Answer 4

Remember to include the contentType property in your ajax call, and utilize the JSON.stringify method to construct the JSON data for posting. Make sure to set the type as POST, allowing MVC Model binding to automatically bind the posted data to your class object.

var filter = { "Filtro": { "Codigo": "_1", "Descricao": "TESTE" }, 
                                               "page": "1", "pageSize": "10" }; 
$.ajax({
    url: fullUrl,
    type: 'POST',
    dataType: 'json',
    contentType: 'application/json',
    data: JSON.stringify(filter),
    success: function (result) {
        alert(result.Data.length);
        self.Parametros(result.Data);
    }
});

Answer 5

Answer №3

Another method to retrieve POST variables is by utilizing the Newtonsoft.Json.Linq JObject library.

Let's consider the following POST request:

$.ajax({
    type: 'POST',
    url: 'API URL',
    data: { 'Note': noteContent, 'Story': storyContent },
    dataType: 'text',
    success: function (responseData) { }
});

In an APIController, these variables can be accessed as shown below:

public void UpdateInfo([FromBody]JObject postData)
{
    var Note = (String)postData["Note"];
    var Story = (String)postData["Story"];
}

Answer 6

Another method to retrieve POST variables is by utilizing the Newtonsoft.Json.Linq JObject library.

Let's consider the following POST request:

$.ajax({
    type: 'POST',
    url: 'API URL',
    data: { 'Note': noteContent, 'Story': storyContent },
    dataType: 'text',
    success: function (responseData) { }
});

In an APIController, these variables can be accessed as shown below:

public void UpdateInfo([FromBody]JObject postData)
{
    var Note = (String)postData["Note"];
    var Story = (String)postData["Story"];
}

Answer 7

Answer №4

By appending JSON data to the query string and parsing it later on the web API side, you can handle complex objects as well. This method proves to be more useful than posting a JSON object, especially in cases where there are specific requirements for HTTP GET requests.

//JavaScript code
    var data = { UserID: "10", UserName: "Long", AppInstanceID: "100", ProcessGUID: "BF1CC2EB-D9BD-45FD-BF87-939DD8FF9071" };
    var request = JSON.stringify(data);
    request = encodeURIComponent(request);

    doAjaxGet("/ProductWebApi/api/Workflow/StartProcess?data=", request, function (result) {
        window.console.log(result);
    });

    //Web API file:
    [HttpGet]
    public ResponseResult StartProcess()
    {
        dynamic queryJson = ParseHttpGetJson(Request.RequestUri.Query);
            int appInstanceID = int.Parse(queryJson.AppInstanceID.Value);
        Guid processGUID = Guid.Parse(queryJson.ProcessGUID.Value);
        int userID = int.Parse(queryJson.UserID.Value);
        string userName = queryJson.UserName.Value;
    }

    //Utility function:
    public static dynamic ParseHttpGetJson(string query)
    {
        if (!string.IsNullOrEmpty(query))
        {
            try
            {
                var json = query.Substring(7, query.Length - 7); //separating ?data= characters
                json = System.Web.HttpUtility.UrlDecode(json);
                dynamic queryJson = JsonConvert.DeserializeObject<dynamic>(json);

                return queryJson;
            }
            catch (System.Exception e)
            {
                throw new ApplicationException("Unable to deserialize object due to incorrect string content！", e);
            }
        }
        else
        {
            return null;
        }
    }

Answer 8

By appending JSON data to the query string and parsing it later on the web API side, you can handle complex objects as well. This method proves to be more useful than posting a JSON object, especially in cases where there are specific requirements for HTTP GET requests.

//JavaScript code
    var data = { UserID: "10", UserName: "Long", AppInstanceID: "100", ProcessGUID: "BF1CC2EB-D9BD-45FD-BF87-939DD8FF9071" };
    var request = JSON.stringify(data);
    request = encodeURIComponent(request);

    doAjaxGet("/ProductWebApi/api/Workflow/StartProcess?data=", request, function (result) {
        window.console.log(result);
    });

    //Web API file:
    [HttpGet]
    public ResponseResult StartProcess()
    {
        dynamic queryJson = ParseHttpGetJson(Request.RequestUri.Query);
            int appInstanceID = int.Parse(queryJson.AppInstanceID.Value);
        Guid processGUID = Guid.Parse(queryJson.ProcessGUID.Value);
        int userID = int.Parse(queryJson.UserID.Value);
        string userName = queryJson.UserName.Value;
    }

    //Utility function:
    public static dynamic ParseHttpGetJson(string query)
    {
        if (!string.IsNullOrEmpty(query))
        {
            try
            {
                var json = query.Substring(7, query.Length - 7); //separating ?data= characters
                json = System.Web.HttpUtility.UrlDecode(json);
                dynamic queryJson = JsonConvert.DeserializeObject<dynamic>(json);

                return queryJson;
            }
            catch (System.Exception e)
            {
                throw new ApplicationException("Unable to deserialize object due to incorrect string content！", e);
            }
        }
        else
        {
            return null;
        }
    }

Answer 9

Answer №5

When working with .NET Core, it's important to note that the HttpClient automatically sets the transfer-encoding: chunked header, which may result in null parameters for your .NET Web API controller.

To resolve this issue, you can manually set the ContentLength header like so:

var json = JsonConvert.SerializeObject(myObject);
var content = new StringContent(json, Encoding.UTF8, "application/json");
content.Headers.ContentLength = json.Length;
var response = await client.PostAsync("http://my-api.com", content);

If you're already aware of the problem with the transfer-encoding header, you can find a solution on Stack Overflow here: How to disable Chunked Transfer Encoding in ASP.Net C# using HttpClient

Additionally, there is a related bug report that sheds light on the issue and why it won't be fixed: https://github.com/dotnet/runtime/issues/30283

Answer 10

When working with .NET Core, it's important to note that the HttpClient automatically sets the transfer-encoding: chunked header, which may result in null parameters for your .NET Web API controller.

To resolve this issue, you can manually set the ContentLength header like so:

var json = JsonConvert.SerializeObject(myObject);
var content = new StringContent(json, Encoding.UTF8, "application/json");
content.Headers.ContentLength = json.Length;
var response = await client.PostAsync("http://my-api.com", content);

If you're already aware of the problem with the transfer-encoding header, you can find a solution on Stack Overflow here: How to disable Chunked Transfer Encoding in ASP.Net C# using HttpClient

Additionally, there is a related bug report that sheds light on the issue and why it won't be fixed: https://github.com/dotnet/runtime/issues/30283

An ApiController parameter is receiving a null value for a complex type

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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