linq group by 多列值实现

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#linq #string #list #query #object #class

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本文展示了如何使用C#的LINQ查询来根据`Name`和`BatNum`字段对`TestData`对象列表进行分组，并将相同组内的`Count`字段求和。通过创建匿名类型实例来获取分组后的结果，并通过`Response.Write`显示最终的聚合数据。

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场景是：

//这么一个LIST，最终想得到的结果如下： List<TestData> list = new List<TestData>(); list.Add(new TestData() { Name="A", Count=3,BatNum="001"}); list.Add(new TestData() { Name = "A", Count = 3,BatNum="001" }); list.Add(new TestData() { Name = "A", Count = 3, BatNum = "002" }); list.Add(new TestData() { Name = "b", Count = 3, BatNum = "001" }); list.Add(new TestData() { Name = "b", Count = 6, BatNum = "002" }); list.Add(new TestData() { Name = "b", Count = 3, BatNum = "003" }); list.Add(new TestData() { Name = "b", Count = 5, BatNum = "001" });

最后结果:
Name="A", Count=6,BatNum="001"
Name="A", Count=3,BatNum="002"
Name="b", Count=8,BatNum="001"
Name="b", Count=6,BatNum="002"
Name="b", Count=3,BatNum="003"

实现：

public class TestData { public string Name{get;set;} public int Count { get; set; } public string BatNum { get; set; } } protected void Click(object sender, EventArgs e) { List<TestData> list = new List<TestData>(); list.Add(new TestData() { Name = "A", Count = 3, BatNum = "001" }); list.Add(new TestData() { Name = "A", Count = 3, BatNum = "001" }); list.Add(new TestData() { Name = "A", Count = 3, BatNum = "002" }); list.Add(new TestData() { Name = "b", Count = 3, BatNum = "001" }); list.Add(new TestData() { Name = "b", Count = 6, BatNum = "002" }); list.Add(new TestData() { Name = "b", Count = 3, BatNum = "003" }); list.Add(new TestData() { Name = "b", Count = 5, BatNum = "001" }); var query = from l in list group l by new { l.Name, l.BatNum } into g select new { Name = g.Key.Name, Count = g.Sum(a => a.Count), BatNum = g.Key.BatNum }; string result = ""; foreach (var q in query) { result += "Name=/"" + q.Name + "/"," + "Count=/"" + q.Count + "/"," + "BatNum=/"" + q.BatNum + " /"<br />"; } Response.Write(result); } //结果： Name="A",Count="6",BatNum="001 " Name="A",Count="3",BatNum="002 " Name="b",Count="8",BatNum="001 " Name="b",Count="6",BatNum="002 " Name="b",Count="3",BatNum="003 "