Multiple expands, nested in another expand, produce a wrong query string.

[casually-creative]

When nesting multiple expands inside another expand, the resulting odata query string contains multiple $expand tags in that nest, whilst they should be grouped into one $expand with comma seperated entity references.

Here is an invented code sample:

string oDataQuery = new ODataQueryBuilder()
    .For<RootEntity>("root_entity")
    .ByList()
    .Expand(er => er
        .For<MainRelatedEntity>(root => root.SomeListProperty)
        .Expand(em => em
            .For<SubRelatedEntity1>(main => main.SubProperty1)
            .Select(sub1 => sub1.some_property)
        )
        .Expand(em => em
            .For<SubRelatedEntity2>(main => main.SubProperty2)
            .Select(sub2 => sub2.some_property)
        )
    )
    .ToUri()
    .ToString();

The result of this looks like:

root_entity?$expand=SomeListProperty($expand=SubRelatedEntity1($select=some_property);$expand=SubRelatedEntity2($select=some_property))

while it should be this:

root_entity?$expand=SomeListProperty($expand=SubRelatedEntity1($select=some_property),SubRelatedEntity2($select=some_property))

When sending the first request to my oData endpoint, it obviously ignores the first sub expand, and only takes into account the last one.

---

When expanding multiple relations on the root level, so without the nesting inside the MainRelatedEntity, then it works as expected. The key here is that they are nested.

[tiggris]

HI!

It looks like ODataQueryExpand should be implemented with _hasMultyExpands:

public IODataQueryExpand<TEntity> Expand(Expression<Func<TEntity, object>> expandNested)
{
    var query = new ODataOptionExpandExpressionVisitor().ToQuery(expandNested);

    Expand(query);

    return this;
}

public IODataQueryExpand<TEntity> Expand(Action<IODataExpandResource<TEntity>> expandNested)
{
    var builder = new ODataExpandResource<TEntity>(_odataQueryBuilderOptions);

    expandNested(builder);

    Expand(builder.Query);
    
    return this;
}

...

private IODataQueryExpand<TEntity> Expand<T>(T query) where T : class
{
    if (_hasMultyExpands)
    {
        _stringBuilder.Merge(ODataOptionNames.Expand, QuerySeparators.Nested, $"{QuerySeparators.Comma}{query}");
    }
    else
    {
        _stringBuilder.Append($"{ODataOptionNames.Expand}{QuerySeparators.EqualSign}{query}{QuerySeparators.Nested}");
    }

    _hasMultyExpands = true;

    return this;
}

[tiggris]

@ZEXSM I've created a fix - please let me know if you would like me to share it :)