ArgumentException: Unterminated string passed in - asp.net

Question

I recently encountered this error in one of the pages in my site.
[ArgumentException: Unterminated string passed in. (26): {"selectedIndexes":["0"],"]
at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeString()
at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeMemberName()
at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeDictionary(Int32\ depth)
at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeInternal(Int32\ depth)
at System.Web.Script.Serialization.JavaScriptObjectDeserializer.BasicDeserialize(String\ input, Int32 depthLimit, JavaScriptSerializer serializer)
at System.Web.Script.Serialization.JavaScriptSerializer.Deserialize(JavaScriptSerializer\ serializer, String input, Type type, Int32 depthLimit)
at System.Web.Script.Serialization.JavaScriptSerializer.DeserializeObject(String\ input)
at Telerik.Web.UI.RadCompositeDataBoundControl.LoadPostData(String postDataKey,\ NameValueCollection postCollection)
at Telerik.Web.UI.RadCompositeDataBoundControl.System.Web.UI.IPostBackDataHandler.LoadPostData(String\ postDataKey, NameValueCollection postCollection)
at System.Web.UI.Page.ProcessPostData(NameValueCollection postData, Boolean\ fBeforeLoad)
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint,\ Boolean includeStagesAfterAsyncPoint)
[HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown.]
at System.Web.UI.Page.HandleError(Exception e)
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint,\ Boolean includeStagesAfterAsyncPoint)
at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint,\ Boolean includeStagesAfterAsyncPoint)
at System.Web.UI.Page.ProcessRequest()
at System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context)
at System.Web.UI.Page.ProcessRequest(HttpContext context)
at ASP.pages_appeal_appealaction_aspx.ProcessRequest(HttpContext context)
at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
What could be the reason for this exception ? Any ideas how to solve it ??

Answer 1

Yep. This error happens when the ASP.NET system receives a request, routes it to your handler and ModelBinder takes over to map values passed in to parameters in your handler. When one of those parms is a string and that string is started but not terminated, it throws the System.ArgumentException from the System.String.DeserializeString() method.
You have two options.
Fix the string data on the browser in JavaScript before you send it. (duh).
Create a custom Model Binder to handle the exception gracefully and send back a 500-series HTTP error or better yet, fix the data in a predictable way. That fixing is not always possible like in a sound file, image, movie or other base64-encoded blob.
Here's how to do #2 - Creating a custom model binder.