Why I am getting the 500 error only when I am posting the data to web api?

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C#3.5

WebAPI

AngularJs

Hi I am trying to post data to web api I am getting 500 error and method is not being called . The code is below

This is the Model class

public class Category
  {
      public int CategoryId { get; set; }
      public string CategoryName { get; set; }
      public string ParentCategoryId { get; set; }
      public string IsServiceContainer { get; set; }
      public string ImageUrl { get; set; }
      public string Description { get; set; }
      public List<Category> ChildCategories { get; set; }
      public string IsActive { get; set; }
  }

This is the controller Method

[ResponseType(typeof(Category))]
     public IHttpActionResult PostCategory(Category category)
     {
         if (!ModelState.IsValid)
         {
             return BadRequest(ModelState);
         }
         ObDataAccess.InsertCategory(category.CategoryName, category.ImageUrl, category.ParentCategoryId, category.IsActive, category.Description, category.IsServiceContainer);
         return CreatedAtRoute("DefaultApi", new { id = category.CategoryId }, category);
     }

this is the Angular js Service

/// <reference path="D:\FetotAdmin\FetotAdmin\FetotAdmin\Scripts/angular.js" />
var CategoryService = angular.module('CategoryService', []);
CategoryService.factory('CategoryApi', function ($http) {
    var urlBase = "http://localhost:60624/api";
    var CategoryApi = {};
    CategoryApi.getCategorees = function () {
        return $http.get(urlBase + '/Category');

    };
    CategoryApi.AddCategory = function (category) {
        alert(JSON.stringify(category));
        //var req = $http({
        //    method: 'post',
        //    url: urlBase + '/Category',
        //    data: category

        //});
        //return req;

        return $http.post('http://localhost:60624/api/Category/', category);
    };
    return CategoryApi;

});

What I have tried:

I tried with $http.post method. when I am calling the web api created with Entity framework it is working fine but when I am calling self created web api with post operation its giving 500 error only in case of post data