Question

我有一张桌子，我想总结一下重复的行：

|name  | n |   |name  | n |
|------+---|   |------+---|
|leo   | 1 |   |leo   | 3 |
|wayne | 1 |   |wayne | 2 |
|joe   | 1 |   |joe   | 1 |
|wayne | 1 |
|leo   | 1 |
|leo   | 1 |

我可以像这样删除它，但如何总结？

        ArrayList UniqueRecords = new ArrayList();
        ArrayList DuplicateRecords = new ArrayList();

        foreach (DataRow dRow in table.Rows)
        {
            if (UniqueRecords.Contains(dRow["name"]))
                DuplicateRecords.Add(dRow);
            else
                UniqueRecords.Add(dRow["name"]);
        }

        foreach (DataRow dRow in DuplicateRecords)
        {
            table.Rows.Remove(dRow);
        }

Answer 1

这是你用字典做的。基本上你从＆＃34; name＆＃34;创建一个字典。到DataRow对象，然后总结DataRows＆＃39; ＆＃34; N＆＃34;属性：

// create intermediate dictionary to group the records
Dictionary<string, DataRow> SummarizedRecords = new Dictionary<string, DataRow>();

// iterate over all records 
foreach(DataRow dRow in table.Rows)
{
  // if the record is in the dictionary already -> sum the "n" value
  if(SummarizedRecords.ContainsKey(dRow["name"]))
  {
    SummarizedRecords[dRow["name"]].n += dRow["n"];
  }
  else
  {
    // otherwise just add the element
    SummarizedRecords[dRow["name"]] = dRow;
  }
}

// transform the dictionary back into a list for further usage
ArrayList<DataRow> summarizedList = SummarizedRecords.Values.ToList();

我认为这可以通过 LINQ 更优雅地完成（1行代码）。让我再考虑一下：）

修改

这是一个Linq版本，但是它涉及创建新的DataRow对象，这可能不是你的意图 - 不知道：

ArrayList<DataRow> summarizedRecords = table.Rows.GroupBy(row => row["name"]) // this line groups the records by "name" .Select(group => { int sum = group.Sum(item => item["n"]); // this line sums the "n"'s of the group DataRow newRow = new DataRow(); // create a new DataRow object newRow["name"] = group.Key; // set the "name" (key of the group) newRow["n"] = sum; // set the "n" to sum return newRow; // return that new DataRow }) .ToList(); // make the resulting enumerable a list

Answer 2

感谢您的回复，另一个变种：

var result = from row in table.AsEnumerable()
                             group row by row.Field<string>("Name") into grp
                             select new
                             {
                                 name = grp.Key,
                                 n = grp.Count()
                             };

c＃ - 汇总datatable中的重复行

2 个答案: