Recently, I faced this problem. When the data from my client side is more than 5 MB, it does not hit my MVC Controller; instead, it steps out and shows an error because it has exceeded the max JSON length.

But finally, I got the solution. So, I thought I should share it so that more people can benefit. There are basically 3 steps to do that.

Step1

Set in the webconfig file,

<add key="aspnet:MaxJsonDeserializerMembers" value="550000"/>

Step2

Add the below code in app_start folder, or just download the attached file and paste it in your app_start folder.
  1. public sealed class CustomJsonValueProviderFactory : ValueProviderFactory
  2. {
  3. public override IValueProvider GetValueProvider(ControllerContext controllerContext)
  4. {
  5. if (controllerContext == null)
  6. {
  7. throw new ArgumentNullException("controllerContext");
  8. }
  10. var jsonData = GetDeserializedObject(controllerContext);
  11. if (jsonData == null)
  12. {
  13. return null;
  14. }
  16. var backingStore = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
  17. var backingStoreWrapper = new EntryLimitedDictionary(backingStore);
  18. AddToBackingStore(backingStoreWrapper, String.Empty, jsonData);
  19. return new DictionaryValueProvider<object>(backingStore, CultureInfo.CurrentCulture);
  20. }
  22. private static void AddToBackingStore(EntryLimitedDictionary backingStore, string prefix, object value)
  23. {
  24. var d = value as IDictionary<string, object>;
  25. if (d != null)
  26. {
  27. foreach (var entry in d)
  28. {
  29. AddToBackingStore(backingStore, MakePropertyKey(prefix, entry.Key), entry.Value);
  30. }
  31. return;
  32. }
  34. var l = value as IList;
  35. if (l != null)
  36. {
  37. for (var i = 0; i < l.Count; i++)
  38. {
  39. AddToBackingStore(backingStore, MakeArrayKey(prefix, i), l[i]);
  40. }
  41. return;
  42. }
  44. // primitive
  45. backingStore.Add(prefix, value);
  46. }
  48. private static object GetDeserializedObject(ControllerContext controllerContext)
  49. {
  50. if (
  51. !controllerContext.HttpContext.Request.ContentType.StartsWith("application/json",
  52. StringComparison.OrdinalIgnoreCase))
  53. {
  54. // not JSON request
  55. return null;
  56. }
  58. var reader = new StreamReader(controllerContext.HttpContext.Request.InputStream);
  59. var bodyText = reader.ReadToEnd();
  60. if (String.IsNullOrEmpty(bodyText))
  61. {
  62. // no JSON data
  63. return null;
  64. }
  66. var serializer = new JavaScriptSerializer {MaxJsonLength = int.MaxValue};
  68. var jsonData = serializer.DeserializeObject(bodyText);
  69. return jsonData;
  70. }
  72. private static string MakeArrayKey(string prefix, int index)
  73. {
  74. return prefix + "[" + index.ToString(CultureInfo.InvariantCulture) + "]";
  75. }
  77. private static string MakePropertyKey(string prefix, string propertyName)
  78. {
  79. return (String.IsNullOrEmpty(prefix)) ? propertyName : prefix + "." + propertyName;
  80. }
  82. private class EntryLimitedDictionary
  83. {
  84. private readonly IDictionary<string, object> _innerDictionary;
  85. private int _itemCount;
  87. public EntryLimitedDictionary(IDictionary<string, object> innerDictionary)
  88. {
  89. _innerDictionary = innerDictionary;
  90. }
  92. public void Add(string key, object value)
  93. {
  94. if (++_itemCount > MaximumDepth)
  95. {
  96. throw new InvalidOperationException(
  97. "The length of the string exceeds the value set on the maxJsonLength property.");
  98. }
  100. _innerDictionary.Add(key, value);
  101. }
  103. private static int GetMaximumDepth()
  104. {
  105. var appSettings = ConfigurationManager.AppSettings;
  107. var valueArray = appSettings.GetValues("aspnet:MaxJsonDeserializerMembers");
  108. if (valueArray != null && valueArray.Length > 0)
  109. {
  110. int result;
  111. if (Int32.TryParse(valueArray[0], out result))
  112. {
  113. return result;
  114. }
  115. }
  117. return 1000; // Fallback default
  118. }
  120. private static readonly int MaximumDepth = GetMaximumDepth();
  121. }
  122. }
Step 3

Add the following code in global.asax under protected void Application_Start() for a better appearance. I have removed the other code.
  1. protected void Application_Start()
  2. {
  4. // Increase max Json length
  5. foreach (var factory in ValueProviderFactories.Factories)
  6. {
  7. if (factory is JsonValueProviderFactory)
  8. {
  9. ValueProviderFactories.Factories.Remove(factory as JsonValueProviderFactory);
  10. break;
  11. }
  12. }
  13. ValueProviderFactories.Factories.Add(new CustomJsonValueProviderFactory());
  15. }
Thats all.