/// <summary>
 /// Initializes a new instance of the ODataQuery class.
 /// </summary>
 /// <param name="provider">A provider that implements the <see cref="IQueryProvider"/> contract.</param>
 /// <param name="expression">An OData <see cref="Expression"/>.</param>
 public ODataQuery(ODataQueryProvider <T> provider, Expression expression)
     : this(provider)
 {
     this.expression = expression;
 }
 /// <summary>
 /// Initializes a new instance of the ODataQuery class.
 /// </summary>
 /// <param name="provider">A provider that implements the <see cref="IQueryProvider"/> contract.</param>
 public ODataQuery(ODataQueryProvider <T> provider)
 {
     this.provider   = provider;
     this.expression = Expression.Constant(this);
 }