Solution for your Errors and Exceptions

Cause of Error .NET detected something in entered text which looked like an html statement. ASP.Net By default validates all input controls for potentially unsafe contents that can lead to Cross Site Scripting and SQL Injections. So ASP.Net is not allowing this content so it's blocking by this exception. By default it is recommended to allow this check to happen on each postback. Solution So you can avoid this exception by adding below line <% @   Page   Language ="C#"   AutoEventWireup ="true"   ValidateRequest   =   "false" it will disable the request validation for current page. if you want to disable for whole application then you can put in web.config as below in system.Web section. < pages   validateRequest  = " false "  /> For .Net 4.0 or higher versions write below code under System.Web section. < httpRuntime  requestValidationMode  =  " 2.0 "  />

If you return any thing from method instead of void then you must return the defined type value as described in return type. Case 1 . If you are using for , while loop or any other conditional statement then you should use return statement in all places like below. public static bool isTwenty( int num)         {             for ( int j = 1; j <= 20; j++)             {                 if (num % j != 0)                 {                     return false ;                 }                 else if (num % j == 0 && num == 20)                 {                     return true ;                 }             }             return false ;         } Case 2. If you are using Try Catch then Give return or throw in both try and catch Or give in finally only as below. put return or throw in Try and catch both public int display() {             int x = 0;             int y = 10;             try             {           

Solution -  When you get 2 calls in WCF service that means there is serialization problem in your code. it may be in Data Member or some other issue related to Serialization.

Solution -  For this type of problem you should use same assembly version number in web.config file and add same version assembly in add reference  and use same version assembly in aspx page <%@ Register assembly="Infragistics4.Web.v13.1, Version=13.1.20131.2157, Culture=neutral, PublicKeyToken=7dd5c3163f2cd0cb" namespace="Infragistics.Web.UI.GridControls" tagprefix="igtbl" %> then version number defined above  13.1.20131.2157 should be same at below three places. Web.config File Add Reference Aspx Page

Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property. Solution Set the MaxJsonLength property in web.config or controller as below. <system.web.extensions> <scripting> <webServices> <jsonSerialization maxJsonLength = "2147483644" /> </webServices> </scripting> </system.web.extensions> If it does not work then try to write like below. public ActionResult ControllerAction () { var jsonResult = Json ( veryLargeCollection , JsonRequestBehavior . AllowGet ); jsonResult . MaxJsonLength = int . MaxValue ; return jsonResult ; } If with above code still you are getting this error then use NewtonSoft.Json code. public   JsonResult   ControllerAction ( )         {              var  data= service.LoadData();              var  searializeddata =  JsonConvert .SerializeObject(data);