Question

如何以下列方式为List类型属性执行OrderBy？

我想按照名字和名单中的第一个字符串排序

UnOrdered：ResearcherNames

Zoe Las，Joe Smith

Kyle Burt

Adam Zing

Ordered：ResearcherNames

Adam Zing

Kyle Burt

Zoe Las，Joe Smith

以下是我班级的样子

public class assignments
{
    public List<string> ReseacherNames { get; set; }
    public List<string> ClientUserNames { get; set; }
    ------Other Properties ------
}

 //fill list
 combinedAssignments = new List<assignments>();
 foreach(var item in db) 
 {
    combinedAssingments.Add(item)
 }

 //need to sort by ResearcherNames
 combinedAssignments = combinedAssignments.OrderBy(x => x.ReseacherNames ).ToList();

当我使用上面的OrderBy调用运行时，我得到“至少有一个对象必须实现IComparable”。错误。

尝试

所以我意识到我必须使用IComparer for List类型并且已经实现了如下的比较器：

 public class RecordComparer : IComparer<List<string>>
 {
        public int Compare(string x, string y)
        {
            if (x == null)
            {
                if (y == null)
                {
                    // If x is null and y is null, they're 
                    // equal.  
                    return 0;
                }
                else
                {
                    // If x is null and y is not null, y 
                    // is greater.  
                    return -1;
                }
            }
            else
            {
                // If x is not null... 
                // 
                if (y == null)
                // ...and y is null, x is greater.
                {
                    return 1;
                }
                else
                {
                    // ...and y is not null, compare the  
                    // lengths of the two strings. 
                    // 
                    int retval = x.Length.CompareTo(y.Length);

                    if (retval != 0)
                    {
                        // If the strings are not of equal length, 
                        // the longer string is greater. 
                        // 
                        return retval;
                    }
                    else
                    {
                        // If the strings are of equal length, 
                        // sort them with ordinary string comparison. 
                        // 
                        return x.CompareTo(y);
                    }
                }
            }
        }

        public int Compare(List<string> x, List<string> y)
        {
            var result = 0;
            if ((x != null && x.Count>0 )&& ( y != null && y.Count>0) )
            {

                return Compare(x[0], y[0]);
            }

            return result;
        }
    }
}

用法：

var rc = new RecordComparer();
 combinedAssignments = combinedAssignments.OrderBy(x=>     x.ResearcherNames,rc).ToList();

没有错误消息，但结果未按字母排序。

Answer 1

不需要IComparer。这将按照第一个研究人员的名字顺序为您提供作业：

combinedAssignments = combinedAssignments
  .OrderBy(x => x.ReseacherNames.FirstOrDefault())
  .ToList();

OrderBy在List <string>属性上

1 个答案: