/// <summary>
/// Returns a CqlQuery which after execution will return the first element of a sequence,
/// or a default value if the sequence contains no elements.
/// To execute this CqlQuery use <c>Execute()</c> method.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <param name="source">The CqlQuery<TSource> to return the first element of.</param>
/// <returns><c>a CqlQuery<TSource> which after execution will return default(TSource)</c> if source is empty,
/// otherwise the first element in source.</returns>
public static CqlQuerySingleElement <TSource> FirstOrDefault <TSource>(this CqlQuery <TSource> source)
{
var ret = new CqlQuerySingleElement <TSource>(source.Table.CreateQuery <TSource>(Expression.Call(
null, CqlMthHelps.FirstOrDefaultMi,
new[] { source.Expression, Expression.Constant(1) })).Expression, source);
source.CopyQueryPropertiesTo(ret);
return(ret);
}
/// <summary>
/// Returns a CqlQuery which after execution will return the first element of the sequence that satisfies a condition
/// or a default value if no such element is found.
/// To execute this CqlQuery use <c>Execute()</c> method.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <param name="source">The Table<TSource> to return the first element of.</param>
/// <param name="predicate">A function to test each element for a condition.</param>
/// <returns>a CqlQuery<TSource> which after execution will return <c>default(TSource)</c> if source is empty
/// or if no element passes the test specified by predicate,
/// otherwise the first element in source that passes the test specified by predicate.</returns>
public static CqlQuerySingleElement <TSource> FirstOrDefault <TSource>(this Table <TSource> source, Expression <Func <TSource, bool> > predicate)
{
var ret = new CqlQuerySingleElement <TSource>(source.Table.CreateQuery <TSource>(Expression.Call(
null, CqlMthHelps.FirstOrDefault_ForCQLTableMi,
new[] { source.Expression, Expression.Constant(1), predicate })).Expression, source);
source.CopyQueryPropertiesTo(ret);
return(ret);
}