Ajax errors

Hi I am getting this error a lot lately. Can someone please explain what is the problem?

System.Web.HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.IO.FileLoadException: Could not load file or assembly 'AjaxControlToolkit, Version=3.0.20229.38756, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040) File name: 'AjaxControlToolkit, Version=3.0.20229.38756, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e' at System.Reflection.Assembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection) at System.Reflection.Assembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection) at System.Reflection.Assembly.InternalLoad(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection) at System.Reflection.Assembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection) at System.Reflection.Assembly.Load(String assemblyString) at AjaxControlToolkit.ToolkitScriptManager.DeserializeScriptEntries(String serializedScriptEntries, Boolean loaded) at AjaxControlToolkit.ToolkitScriptManager.OutputCombinedScriptFile(HttpContext context) at AjaxControlToolkit.ToolkitScriptManager.OnInit(EventArgs e) at System.Web.UI.Control.InitRecursive(Control namingContainer) at System.Web.UI.Control.InitRecursive(Control namingContainer) at System.Web.UI.Control.InitRecursive(Control namingContainer) at System.Web.UI.Control.InitRecursive(Control namingContainer) at System.Web.UI.Control.InitRecursive(Control namingContainer) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) === Pre-bind state information === LOG: User = NT AUTHORITY\NETWORK SERVICE LOG: DisplayName = AjaxControlToolkit, Version=3.0.20229.38756, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e (Fully-specified) LOG: Appbase = file:///.../wwwroot/ LOG: Initial PrivatePath = ...\wwwroot\bin Calling assembly : AjaxControlToolkit, Version=3.0.30512.20315, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e. === LOG: This bind starts in default load context. LOG: Using application configuration file: ...wwwroot\web.config LOG: Using host configuration file: \\?\C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\aspnet.config LOG: Using machine configuration file from C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\config\machine.config. LOG: Post-policy reference: AjaxControlToolkit, Version=3.0.20229.38756, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e LOG: Attempting download of new URL file:///C:/WINDOWS/Microsoft.NET/Framework/v2.0.50727/Temporary ASP.NET Files/root/144f0309/507ea4f8/AjaxControlToolkit.DLL. LOG: Attempting download of new URL file:///C:/WINDOWS/Microsoft.NET/Framework/v2.0.50727/Temporary ASP.NET Files/root/144f0309/507ea4f8/AjaxControlToolkit/AjaxControlToolkit.DLL. LOG: Attempting download of new URL file:///.../wwwroot/bin/AjaxControlToolkit.DLL. WRN: Comparing the assembly name resulted in the mismatch: Revision Number ERR: Failed to complete setup of assembly (hr = 0x80131040). Probing terminated. --- End of inner exception stack trace --- 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 includeStagesAfterAsyncP

the file the error says is missing... is missing.

its saying ajaxtoolkit is missing but thats in my bin folder!

did you check the version number?

Nice catch, there is a difference in version number. But when I upload previous version the website doesn't work and when I upload the latest ajex, the website works but it throws this error.
Where do I change that? web config is of latest nopcommerce version.

the way i do it is I put any control from the ajaxtoolkit into a page, and then delete the control. your web.config should then have the reference to the correct assembly.