Following error comes when creating a WebPart In sharePoint 2010 Server.
Web Part Error: Unhandled exception was thrown by the user code wrapper's Execute method in the partial trust app domain: System.Web.HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.TypeLoadException: Could not load type 'Microsoft.SharePoint.WebControls.SPGridView' from assembly 'Microsoft.SharePoint, Version=14.900.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c'. at ListMenuSample.ListMenuSample.ListMenuSample.CreateChildControls() at System.Web.UI.Control.EnsureChildControls() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) --- 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 includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest() at System.Web.UI.Page.ProcessRequest(HttpContext context) at Microsoft.SharePoint.UserCode.SPUserCodeWebPartWrapper.ExecuteHttpRequest(SPUserCodeWebPartHttpRequestContext webPartExecutionContext, SPUserCodeWebPartHttpResponse httpRequestResponse) at Microsoft.SharePoint.UserCode.SPUserCodeWebPartWrapper.Execute(SPUserCodeExecutionContext executionContext) at Microsoft.SharePoint.UserCode.SPUserCodeApplicationHostAppDomainRef.Execute(Type userCodeWrapperType, SPUserCodeCachedAssemblyGroup userAssemblyGroup, Guid siteCollectionId, Byte[] binaryUserCodeToken, Byte[] proxyOperationToken, SPUserCodeExecutionContext executionContext)
Thanks & Regards, Basant