/// <summary>
/// Initializes a new instance of the <see cref="FieldSelectionSet" /> class.
/// </summary>
/// <param name="graphType">The graph type this selection set is acting on.</param>
/// <param name="rootPath">The document specific root path under which all fields should be nested in this selection set.</param>
public FieldSelectionSet(IGraphType graphType, SourcePath rootPath)
{
this.GraphType = Validation.ThrowIfNullOrReturn(graphType, nameof(graphType));
_knownFieldAliases = new CharMemoryHashSet();
_fields = new List <FieldSelection>();
Validation.ThrowIfNull(rootPath, nameof(rootPath));
this.RootPath = rootPath.Clone();
}