Export to Excel stopped working

Question

I have two screens that display the same datagrid on one the fields are all lables and the second one has some fields set to be editable.
The second screens export to excel button stopped working in the debugger and I get the following error.
An error occurred while running the screen. You can close the screen or ignore the error and continue using the screen.
Error details: Value cannot be null.
Parameter name: key
I do not get this error on the other screen but always get it on this screen.

Answer 1

I am able to export the same properties form the same entities using a different screen though? Neither screen has an addition queries the other screen does not have the only difference is that other screen uses labels. I did add an allergies table but it
quires the monograms table to get medication names for its table not the other way around. The Monograms table is a simple editable grid related ONE grid to Many Allergies. It has a related property I tried to assign a default to. using the following code
oh I see I had to make the entries in my code required even though I am only exporting them. Weird they were old properties I had long ago made and then used code to get around them having to be required.
It works now cheers
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.LightSwitch;
namespace LightSwitchApplication
public partial class Allergy
partial void AllergySummary_Compute(ref string result)
// handle Nulls
//make some string vars with defaults
string genName = "";
string classSum = "";
string generic = "";
string classification = "";
//set string vars only if Monogram not null
if(Monogram != null)
//use null coalesce operator '??' to convert null properties to string
genName = Monogram.GenericName ?? "None Listed";
classSum = Monogram.ClassificationSummary ?? "No Classification";
generic = " / Generic Drug: ";
classification = " / ";
if (classSum == "")
classification = "";
result = "(Type: " + TypeOfAllergy + generic + genName + classification + classSum + ")";