Reconciling two collections of objects

Question

I have a form where users can modify a collection of objects using a DataGrid. When the form is opened I create a deep copy of the original collection and if the Cancel butt

Answer 1

The way I've dealt with this depends on the collections of objects having a unique ID. I also pass in the repository to deal with this as well, but for brevity I left it out. It's similiar to the following:

public static void MergeFields(IEnumerable persistedValues, IEnumerable newValues)
{
    var leftIds = persistedValues.Select(x => x.Id).ToArray();
    var rightIds = newValues.Select(x => x.Id).ToArray();

    var toUpdate = rightIds.Intersect(leftIds).ToArray();
    var toAdd = rightIds.Except(leftIds).ToArray();
    var toDelete = leftIds.Except(rightIds).ToArray();

    foreach(var id in toUpdate){
        var leftScope = persistedValues.Single(x => x.ID == id);
        var rightScope = newValues.Single(x => x.ID == id);

        // Map appropriate values from rightScope over to leftScope
    }

    foreach(var id in toAdd) {
        var rightScope = newValues.Single(x => x.ID == id);
        // Add rightScope to the repository
    }

    foreach(var id in toDelete) {
        var leftScope = persistedValues.Single(x => x.ID == id);
        // Remove leftScope from the repository
    }

    // persist the repository
}