Fachtagung Abbruch

Value cannot be null. (Parameter 's')   at System.DateTime.ParseExact(String s, String format, IFormatProvider provider)
   at InvokeStub_DateTime.ParseExact(Object, Span`1)
   at System.Reflection.MethodBaseInvoker.InvokeWithFewArgs(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)Exception has been thrown by the target of an invocation.
                  start = parseDate(ViewShortDate, "d.M.yyyy", CultureInfo.InvariantCulture)
                  end = parseDate(ViewEndShortDate, "d.M.yyyy", CultureInfo.InvariantCulture).AddDays(1)
                        #####################################################################
                  for(i=0;start!=end;start=start.AddDays(1))
   at System.Reflection.MethodBaseInvoker.InvokeWithFewArgs(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at TemplateSlang.FunctionCallNode.<>c__DisplayClass3_0.<Visit>b__0() in /home/simon/Documents/siteface/siteface/sitefaceCore/TemplateSlang/TemplateSlangMain.cs:line 929
   at TemplateSlang.FunctionCallNode.Visit(ExecContext e)
   at TemplateSlang.BinaryNode.Visit(ExecContext e) in /home/simon/Documents/siteface/siteface/sitefaceCore/TemplateSlang/TemplateSlangMain.cs:line 1708
   at TemplateSlang.FunctionCallNode.<>c__DisplayClass3_0.<Visit>b__0() in /home/simon/Documents/siteface/siteface/sitefaceCore/TemplateSlang/TemplateSlangMain.cs:line 921
   at TemplateSlang.FunctionCallNode.Visit(ExecContext e)
   at TemplateSlang.AssignNode.Visit(ExecContext e) in /home/simon/Documents/siteface/siteface/sitefaceCore/TemplateSlang/TemplateSlangMain.cs:line 1176
   at TemplateSlang.TplChunk.Visit(ExecContext e) in /home/simon/Documents/siteface/siteface/sitefaceCore/TemplateSlang/TemplateSlangMain.cs:line 3320
Value cannot be null. (Parameter 's')
   at System.DateTime.ParseExact(String s, String format, IFormatProvider provider)
   at InvokeStub_DateTime.ParseExact(Object, Span`1)
   at System.Reflection.MethodBaseInvoker.InvokeWithFewArgs(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)