Question

鉴于KeyValuePair<string, DataRow>，我想迭代通过特定列对每个条目进行分组的条目。

所以如果我们有KeyValuePair<StudentID, Student>。

学生是一个包含几个圆柱学生信息的dataRow，我想按studentName

对我的foreach循环进行排序

我希望能够写出如下内容：

foreach(KeyValuePair<string, DataRow> entry in Students.GroupBy(x => x.value["StudentName"].toString()))

Answer 1

The .GroupBy() LINQ method returns a grouping that contains the list of all the items that fit in that group.

foreach(IGrouping<string, DataRow> entry in Students.GroupBy(x => x.value["StudentName"].toString())) {

    var studentName = entry.Key;
    var studentsWithStudentName = entry.Select(x => x);
}

If your Students collection has a type of ICollection<KeyValuePair<string, DataRow>>, then the studentsWithStudentName field here will have the type:

IEnumerable<KeyValuePair<string, DataRow>>

Of course you could group by any field you like (say student gender) and the grouping will contain a collection of students that match that group. You can even group by generated values, say:

Students.GroupBy(x => x.value["StudentHeight"] > 5)

This would give 2 groups, one where the Key was true where all the students in it have a height greater than 5.

如何GroupBy KeyValuePair的特定列<string，datarow =“”>

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