Server Error in '/' Application.

Object Graph cannot be null.
Parameter name: graph

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.ArgumentNullException: Object Graph cannot be null.
Parameter name: graph

Source Error: 


Line 100:                Response.AddHeader("Content-Disposition", "attachment; filename=\"Projekt1.drb\"");
Line 101:                Response.Flush();
Line 102:                form.Serialize(Response.OutputStream, GProject);
Line 103:                Response.OutputStream.Close();
Line 104:

Source File: c:\web\rheinzink_rinne\Main.aspx.cs    Line: 102

Stack Trace: 


[ArgumentNullException: Object Graph cannot be null.
Parameter name: graph]
   System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Serialize(Object graph, Header[] inHeaders, __BinaryWriter serWriter, Boolean fCheck) +12853708
   System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph, Header[] headers, Boolean fCheck) +137
   System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph) +18
   rinne.MainForm.CheckAction() in c:\web\rheinzink_rinne\Main.aspx.cs:102
   rinne.MainForm.Page_Load(Object sender, EventArgs e) in c:\web\rheinzink_rinne\Main.aspx.cs:42
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +52
   System.Web.UI.Control.OnLoad(EventArgs e) +97
   System.Web.UI.Control.LoadRecursive() +61
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +693

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.8.4718.0