Question

When I run the following test, I get an ArgumentOutOfRangeException:

[TestClass]
public class ReproduceException
{
    [TestMethod]
    public void Doesnt_throw_when_adding_to_grouped_collection()
    {
        var collection = new ListCollectionView(new List<Test>());
        collection.SortDescriptions.Add(new SortDescription("IsTrue", ListSortDirection.Ascending));
        collection.GroupDescriptions.Add(new PropertyGroupDescription("Name"));
        collection.AddNewItem(new Test() { Name = "Bob", IsTrue = false });
        collection.CommitNew();

    }
}

public class Test
{
    public string Name { get; set; }
    public bool IsTrue { get; set; }
}

An I get the following exception:

System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
at System.ThrowHelper.ThrowArgumentOutOfRangeException()
at System.Collections.ObjectModel.Collection`1.RemoveAt(Int32 index)
at System.Windows.Data.ListCollectionView.CommitNewForGrouping()
at System.Windows.Data.ListCollectionView.CommitNew()

Am I perhaps not using the AddNewItem / CommitNew in the right way?

Answer 1

Possible solutions:

1) Do before adding a new item

 collection.NewItemPlaceholderPosition = NewItemPlaceholderPosition.AtBeginning;

2) Basically try out adding items before creation of the Grouping and Sorting:

var collection = new ListCollectionView(new List<Test>());            
collection.AddNewItem(new Test() { Name = "Bob", IsTrue = false });
collection.CommitNew();

collection.SortDescriptions.Add(new SortDescription("IsTrue", 
                                          ListSortDirection.Ascending));   
collection.GroupDescriptions.Add(new PropertyGroupDescription("Name"));

Analysis:

After digging into the .NET Reflector, CommitNew() method has following check:

// !!! When you've added GroupDescription this.IsGrouping becomes true!
if (this.IsGrouping)
{
    this.CommitNewForGrouping();
}

Since you’ve added GroupDescription it would commit for grouping:

private void CommitNewForGrouping()
{
    int num;   

    // !!! I believe it is None by default
    switch (this.NewItemPlaceholderPosition)
    {
        case NewItemPlaceholderPosition.AtBeginning:
            num = 1;
            break;

        case NewItemPlaceholderPosition.AtEnd:
            num = this._group.Items.Count - 2;
            break;

        default:
            // !!! Since you've not added groups -1 would be assigned to num
            num = this._group.Items.Count - 1;
            break;
    }
    int index = this._newItemIndex;
    object item = this.EndAddNew(false);

    // This method will call RemoveAt(num) where num == -1 in your case
    this._group.RemoveSpecialItem(num, item, false);
    this.ProcessCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, 
             item, index));

}

internal void RemoveSpecialItem(int index, object item, bool loading)
{
     ...
     // will fail since index always -1
     base.ProtectedItems.RemoveAt(index);
     ...
}

LCV has private method ProcessCollectionChangedWithAdjustedIndex which adjust index in different scenarios but it is not called whilst adding a new item with Grouping enables, I’m not sure why so looks like this is by design (?!) so you have manually specify placeholder AtBeginning for the new items.