/// <summary>
/// Projects each element of a sequence into a new form.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <typeparam name="TResult">The type of the value returned by selector.</typeparam>
/// <param name="source">A CqlQuery<TSource> which after execution returns a sequence of values to invoke a transform function on.</param>
/// <param name="selector">A transform function to apply to each element.</param>
/// <returns>a CqlQuery<TSource> which after execution will return an IEnumerable<TSource> whose elements
/// are the result of invoking the transform function on each element of source.
/// To execute this CqlQuery use <c>Execute()</c> method.</returns>
public static CqlQuery <TResult> Select <TSource, TResult>(this CqlQuery <TSource> source, Expression <Func <TSource, TResult> > selector)
{
Expression expression = source.Expression;
CqlQuery <TResult> result;
if (typeof(TSource) != typeof(TResult))
{
//Its a client projection of an existent CqlQuery
if (!(source is IClientProjectionCqlQuery))
{
//The SELECT expression changed
expression = Expression.Call(null, CqlMthHelps.SelectMi, new[] { source.Expression, selector });
result = new ClientProjectionCqlQuery <TSource, TResult>(expression, source, selector, true);
}
else
{
//its a client projection of a client projection
//we should use the original source.Expression
result = new ClientProjectionCqlQuery <TSource, TResult>(expression, source, selector, true);
}
}
else
{
expression = Expression.Call(null, CqlMthHelps.SelectMi, new[] { source.Expression, selector });
//Its a mapper based projection
result = (CqlQuery <TResult>)source.Table.CreateQuery <TResult>(expression);
}
source.CopyQueryPropertiesTo(result);
return(result);
}
public static CqlQuery <TResult> Select <TGroup, TSource, TResult>(
this CqlQuery <IGrouping <TGroup, TSource> > source,
Expression <Func <IGrouping <TGroup, TSource>, TResult> > selector)
{
var expression = Expression.Call(null, CqlMthHelps.SelectMi, new[] { source.Expression, selector });
var result = new ClientProjectionCqlQuery <IGrouping <TGroup, TSource>, TResult>(
expression, source, selector, false);
result.CopyQueryPropertiesTo(result);
return(result);
}