I want to get all the rows from table using entity framework but I'm getting error in postman

Question

Visual Studio Code.

namespace MlaWebApi.Controllers
{
    public class PostController : ApiController
    {

        [HttpGet]
        public List<post> PostDescription()
        {

            using (MlaDatabaseDemoEntities context = new MlaDatabaseDemoEntities())
            {
                var postDesc = context.posts.ToList();

                return postDesc;
            }

        }

    }
}

Error in postman:

{ "Message": "An error has occurred.", "ExceptionMessage": "The 'ObjectContent`1' type failed to serialize the response body for content type 'application/json; charset=utf-8'.", "ExceptionType": "System.InvalidOperationException", "StackTrace": null, "InnerException": { "Message": "An error has occurred.", "ExceptionMessage": "The operation cannot be completed because the DbContext has been disposed.", "ExceptionType": "System.InvalidOperationException", "StackTrace": " at System.Data.Entity.Internal.LazyInternalContext.InitializeContext()\r\n at System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType(Type entityType)\r\n at System.Data.Entity.Internal.Linq.InternalSet`1.Initialize()\r\n at System.Data.Entity.Internal.Linq.InternalSet`1.GetEnumerator()\r\n at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)\r\n at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)\r\n at Newtonsoft.Json.Serialization.JsonArrayContract.CreateWrapper(Object list)\r\n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty)\r\n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize(JsonWriter jsonWriter, Object value)\r\n at Newtonsoft.Json.JsonSerializer.SerializeInternal(JsonWriter jsonWriter, Object value)\r\n at System.Net.Http.Formatting.JsonMediaTypeFormatter.<>c__DisplayClassd.b__c()\r\n at System.Threading.Tasks.TaskHelpers.RunSynchronously(Action action, CancellationToken token)" } }