Given a method signature like so...
IEnumerable<Student> get(Func<DataRow, bool> predicate);
How can I pass the predicate argument along to a linq expression?
public override IEnumerable<Student> get(Func<System.Data.DataRow, bool> predicate = null) {
var students = from student in _dataSet.Tables[0].AsEnumerable()
join attendance in _dataSet.Tables[1].AsEnumerable()
on student.Field<int>("id") equals attendance.Field<int>("idStudent")
join grade in _dataSet.Tables[2].AsEnumerable()
on student.Field<int>("id") equals grade.Field<int>("idStudent")
join assignment in _dataSet.Tables[3].AsEnumerable()
on student.Field<int>("id") equals assignment.Field<int>("idStudent")
// where predicate??
// select blahblahblah
// return statement
}
Since predicate
is a function that takes DataRow
as an input -- use it like where predicate(student)
.
var students = from student in _dataSet.Tables[0].AsEnumerable()
...
where predicate == null || predicate(student)
select student
我想你要:
where predicate == null || predicate(student)
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