/// <summary>
/// Add a projection to the query.
/// </summary>
/// <param name="expression">Select method call expression.</param>
private void AddProjection(MethodCallExpression expression)
{
// We only support Select(x => ...) projections. Anything else
// will throw a NotSupportException.
if (expression != null && expression.Arguments.Count == 2)
{
LambdaExpression projection = StripQuote(expression.Arguments[1]) as LambdaExpression;
if (projection != null && projection.Parameters.Count == 1)
{
// Store the type of the input to the projection as we'll
// need that for deserialization of values (since the
// projection will change the expected type of the data
// source)
this.query.ProjectionArgumentType = projection.Parameters[0].Type;
// Compile the projection into a function that we can apply
// to the deserialized value to transform it accordingly.
this.query.Projection = projection.Compile();
// Filter the selection down to just the values used by
// the projection
VisitorHelper.VisitMembers(
projection.Body,
(expr, recur) =>
{
// Ensure we only process members of the parameter
if (expr != null && expr.Expression.NodeType == ExpressionType.Parameter)
{
SerializableMember member = SerializableType.GetMember(expr.Member);
if (member != null)
{
query.Selection.Add(member.Name);
}
}
return(recur(expr));
});
// Make sure we also include all the members that would be
// required for deserialization
foreach (SerializableMember member in
SerializableType.Get(this.query.ProjectionArgumentType)
.Members
.Select(p => p.Value)
.Where(m => m.IsRequired))
{
if (!this.query.Selection.Contains(member.Name))
{
this.query.Selection.Add(member.Name);
}
}
return;
}
}
ThrowForUnsupportedException(expression);
}
/// <summary>
/// Returns the MemberExpressions in the expression hierarchy of the <paramref name="expression"/>.
/// </summary>
/// <param name="expression">The expression to search for children MemberExpressions</param>
/// <returns>A collection of MemberExpressions.</returns>
public IEnumerable <MemberExpression> GetMemberExpressions(Expression expression)
{
List <MemberExpression> members = new List <MemberExpression>();
VisitorHelper.VisitMembers(
expression,
(expr, recur) =>
{
// Ensure we only process members of the parameter
if (expr is MemberExpression)
{
members.Add((MemberExpression)expr);
}
return(recur(expr));
});
return(members);
}
