List is sorted by the specified attribute (implementing the IComparer Interface)

Problem:

There is a List <CourseList> testlist. The class CourseList has five attributes: CourseId, CourseName, CourseStatus, TeacherName, LevelName, and StudentNumber. Now we want to sort testlist by the attributes of the CourseList class.

 

Solution:

 

Define enumeration types for each attribute

public enum CompareType{    CourseId,    CourseName,    CourseStatus,    TeacherName,    LevelName,    StudentNumber}

 

Implement the IComparer Interface

public class CourseListComparer:IComparer<CourseList>{       private CompareType _compareColumn;    public CompareType CompareColumn    {        get { return _compareColumn; }        set { _compareColumn = value; }    }    public CourseListComparer(CompareType t) {        this._compareColumn = t;    }    /// <summary>    /// compare by different property    /// </summary>    /// <param name="x">CourseList x</param>    /// <param name="y">CourseList y</param>    /// <returns>int </returns>    public int Compare(CourseList x,CourseList y) {               switch (this.CompareColumn) {            case CompareType.CourseId:                return x.CourseId.CompareTo(y.CourseId);            case CompareType.CourseName:                return x.CourseName.CompareTo(y.CourseName);            case CompareType.CourseStatus:                return x.CourseStatus.CompareTo(y.CourseStatus);            case CompareType.TeacherName:                return x.TeacherName.CompareTo(y.TeacherName);            case CompareType.LevelName:                return x.LevelName.CompareTo(y.LevelName);            case CompareType.StudentNumber:                return x.StudentNumber.CompareTo(y.StudentNumber);            default: return x.CourseId.CompareTo(y.CourseId);        }    }}

Call the sort method

CourseListComparer courselistComparer = new CourseListComparer(CompareType.CourseId);testList.Sort(courselistComparer);

 

Cause:

List <> in C # has two Sort methods, one with no parameters and the other with the IComparer parameter. The method without parameters is to sort by default comparator. If there are parameters, you must define an IComparer interface.

To implement the ICompare interface, you need to implement the Compare method. The Compare method has two input values to be compared. According to the custom comparison rules, int values are returned. 0 indicates equal, 1 indicates x> y, and-1 indicates x <y.