Server Error in '/' Application.

Object reference not set to an instance of an object.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:


Line 97:                                     <div class="col-md-4 ">
Line 98:                                         <div class="property-image">
Line 99:                                             <a href='<%= ViewState["ClassImg"].ToString() %>' class="image-popup">
Line 100:                                                <img alt="" src='<%= ViewState["ClassImg"].ToString() %>' class="img-fluid z-depth-2"></a>
Line 101:                                            

Source File: c:\WebSites\edusearch.ir\CourseView.aspx    Line: 99

Stack Trace:


[NullReferenceException: Object reference not set to an instance of an object.]
   ASP.courseview_aspx.__RenderContent2(HtmlTextWriter __w, Control parameterContainer) in c:\WebSites\edusearch.ir\CourseView.aspx:99
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +116
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +78
   ASP.mainmaster_master.__Renderform1(HtmlTextWriter __w, Control parameterContainer) in c:\WebSites\edusearch.ir\MainMaster.master:128
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +116
   System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter writer) +11834696
   System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) +46
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +78
   System.Web.UI.HtmlControls.HtmlForm.RenderControl(HtmlTextWriter writer) +49
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +249
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +78
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +249
   System.Web.UI.Page.Render(HtmlTextWriter writer) +38
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +78
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +8752


Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.7.3770.0