c# - 在 mvc4 中使用大量数据进行 ajax 发布期间，系统抛出 System.ArgumentException 异常

Question

我正在执行 ajax post 以在 mvc4 中发布来自 javascript 的数据，但它失败并出现以下异常

string exceeds the value set on the maxJsonLength property.
Parameter name: input
System.ArgumentException: Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property. 

我已经尝试在 web config 中设置配置，但它不起作用

<system.web.extensions>
    <scripting>
        <webServices>
            <jsonSerialization maxJsonLength="2147483647"/>
        </webServices>
    </scripting>
</system.web.extensions>  

我也试过下面的链接，但没有任何效果: http://forums.asp.net/t/1751116.aspx?How+to+increase+maxJsonLength+for+JSON+POST+in+MVC3

var editorText = eval(htmlEditor).GetHtml();     
$.ajax({type: 'POST',
    cache: false,
    contentType: 'application/json; charset=utf-8',
    url: "../Home/SaveExceptionLetter",
    data: JSON.stringify({ message: editorText }),
    datatype: 'json',
    success: function () {
    });
} });

[HttpPost]
[ValidateInput(false)]
public void SaveExceptionLetter(string message){
    //processing this message
}

string exceeds the value set on the maxJsonLength property.
Parameter name: input
System.ArgumentException: Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property.
Parameter name: input
   at System.Web.Script.Serialization.JavaScriptSerializer.Deserialize(JavaScriptSerializer serializer, String input, Type type, Int32 depthLimit)
   at System.Web.Mvc.JsonValueProviderFactory.GetDeserializedObject(ControllerContext controllerContext)
   at System.Web.Mvc.JsonValueProviderFactory.GetValueProvider(ControllerContext controllerContext)
   at System.Web.Mvc.ValueProviderFactoryCollection.<>c__DisplayClassc.<GetValueProvider>b__7(ValueProviderFactory factory)
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at System.Web.Mvc.ValueProviderFactoryCollection.GetValueProvider(ControllerContext controllerContext)
   at System.Web.Mvc.ControllerBase.get_ValueProvider()
   at System.Web.Mvc.ControllerActionInvoker.GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor)
   at System.Web.Mvc.ControllerActionInvoker.GetParameterValues(ControllerContext controllerContext, ActionDescriptor actionDescriptor)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass25.<BeginInvokeAction>b__1e(AsyncCallback asyncCallback, Object asyncState)

Answer 1

嗨@usFarswan 这正是我半小时前遇到的问题，解决方案是http://forums.asp.net/t/1751116.aspx?How+to+increase+maxJsonLength+for+JSON+POST+in+MVC3

您可以像这样实现它，在 global.asax 中添加以下由///***** 指向的行。

namespace MyWebApp
{
    // Note: For instructions on enabling IIS6 or IIS7 classic mode, 
    // visit http://go.microsoft.com/?LinkId=9394801
    public class MvcApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();


            WebApiConfig.Register(GlobalConfiguration.Configuration);
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            XmlConfigurator.Configure();
            DbHelper.getSessionFactory();

            ///// **********
             JsonValueProviderFactory jsonValueProviderFactory = null;

            foreach (var factory in ValueProviderFactories.Factories)
            {
                if (factory is JsonValueProviderFactory)
                {
                    jsonValueProviderFactory = factory as JsonValueProviderFactory;
                }
            }

            //remove the default JsonVAlueProviderFactory
            if (jsonValueProviderFactory != null) ValueProviderFactories.Factories.Remove(jsonValueProviderFactory);

            //add the custom one
            ValueProviderFactories.Factories.Add(new CustomJsonValueProviderFactory());**
       /////*************
        }
    }




     ///********
    public sealed class CustomJsonValueProviderFactory : ValueProviderFactory
    {

        private static void AddToBackingStore(Dictionary<string, object> backingStore, string prefix, object value)
        {
            IDictionary<string, object> d = value as IDictionary<string, object>;
            if (d != null)
            {
                foreach (KeyValuePair<string, object> entry in d)
                {
                    AddToBackingStore(backingStore, MakePropertyKey(prefix, entry.Key), entry.Value);
                }
                return;
            }

            IList l = value as IList;
            if (l != null)
            {
                for (int i = 0; i < l.Count; i++)
                {
                    AddToBackingStore(backingStore, MakeArrayKey(prefix, i), l[i]);
                }
                return;
            }

            // primitive
            backingStore[prefix] = value;
        }

        private static object GetDeserializedObject(ControllerContext controllerContext)
        {
            if (!controllerContext.HttpContext.Request.ContentType.StartsWith("application/json", StringComparison.OrdinalIgnoreCase))
            {
                // not JSON request
                return null;
            }

            StreamReader reader = new StreamReader(controllerContext.HttpContext.Request.InputStream);
            string bodyText = reader.ReadToEnd();
            if (String.IsNullOrEmpty(bodyText))
            {
                // no JSON data
                return null;
            }

            JavaScriptSerializer serializer = new JavaScriptSerializer();
            serializer.MaxJsonLength = int.MaxValue; //increase MaxJsonLength.  This could be read in from the web.config if you prefer
            object jsonData = serializer.DeserializeObject(bodyText);
            return jsonData;
        }

        public override IValueProvider GetValueProvider(ControllerContext controllerContext)
        {
            if (controllerContext == null)
            {
                throw new ArgumentNullException("controllerContext");
            }

            object jsonData = GetDeserializedObject(controllerContext);
            if (jsonData == null)
            {
                return null;
            }

            Dictionary<string, object> backingStore = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
            AddToBackingStore(backingStore, String.Empty, jsonData);
            return new DictionaryValueProvider<object>(backingStore, CultureInfo.CurrentCulture);
        }

        private static string MakeArrayKey(string prefix, int index)
        {
            return prefix + "[" + index.ToString(CultureInfo.InvariantCulture) + "]";
        }

        private static string MakePropertyKey(string prefix, string propertyName)
        {
            return (String.IsNullOrEmpty(prefix)) ? propertyName : prefix + "." + propertyName;
        }
    }
   ///*************
}