DataTable相关：datatable计算功能

看了下大家对datatable的计算功能，搜集了一些例子贴上。

public class DataTableCompute { public static void SomeDataTableCompute() { DataTable myTesttable = new DataTable(); object resultConst = myTesttable.Compute("2*3", "");//计算常量 Console.WriteLine(resultConst); resultConst = myTesttable.Compute("3*2", "false"); Console.WriteLine(resultConst); resultConst = myTesttable.Compute("abs(1)", ""); Console.WriteLine(resultConst); resultConst = myTesttable.Compute("10/2", ""); Console.WriteLine(resultConst); //初始化一个dataTable测试 myTesttable.Columns.Add("id", typeof(string)); myTesttable.Columns.Add("value", typeof(int)); for (int i = 1; i <= 10; i++)//赋值 { System.Data.DataRow dRow = myTesttable.NewRow(); dRow["id"] = "id" + i.ToString(); dRow["value"] = i; myTesttable.Rows.Add(dRow); } //支持以下sql中的函数 resultConst = myTesttable.Compute("count(id)", "false");//求数量 Console.WriteLine(resultConst); resultConst = myTesttable.Compute("count(id)", "true"); Console.WriteLine(resultConst); resultConst = myTesttable.Compute("sum(value)", "");//求和 Console.WriteLine(resultConst); resultConst = myTesttable.Compute("avg(value)", "");//平均 Console.WriteLine(resultConst); resultConst = myTesttable.Compute("min(value)", ""); //最小 Console.WriteLine(resultConst); resultConst = myTesttable.Compute("max(value)", "");//最大 Console.WriteLine(resultConst); resultConst = myTesttable.Compute("StDev(value)", "");//统计标准偏差 Console.WriteLine(resultConst); resultConst = myTesttable.Compute("Var(value)", "");//统计方差 Console.WriteLine(resultConst); resultConst = myTesttable.Compute("max(value)/sum(value)", "");//复杂计算 Console.WriteLine(resultConst); //支持列的操作 DataColumn column = new DataColumn("exp1", typeof(float)); myTesttable.Columns.Add(column); column.Expression = "value*2";//简单计算 resultConst = myTesttable.Select("id='id1'")[0]["exp1"]; Console.WriteLine(resultConst); column.Expression = "len(id)";//字符串函数 resultConst = myTesttable.Select("id='id1'")[0]["exp1"]; Console.WriteLine(resultConst); column.Expression = "len(' '+id+' ')";//字符串函数 resultConst = myTesttable.Select("id='id1'")[0]["exp1"]; Console.WriteLine(resultConst); column.Expression = "len(trim(' '+id+' '))"; resultConst = myTesttable.Select("id='id1'")[0]["exp1"]; Console.WriteLine(resultConst); column.Expression = "substring(id,3,len(id)-2)"; resultConst = myTesttable.Select("id='id1'")[0]["exp1"]; Console.WriteLine(resultConst); column.Expression = "convert(substring(id,3,len(id)-2),'System.Int32')*1.6";//类型转换 resultConst = myTesttable.Select("id='id1'")[0]["exp1"]; Console.WriteLine(resultConst); column.Expression = "isnull(value,10)"; //isnull resultConst = myTesttable.Select("id='id1'")[0]["exp1"]; Console.WriteLine(resultConst); column.Expression = "iif(value>5,1000,2000)"; //三元运算符 resultConst = myTesttable.Select("id='id1'")[0]["exp1"]; Console.WriteLine(resultConst); column.Expression = "iif(id like '%1',1000,2000)"; //like运算符 resultConst = myTesttable.Select("id='id1'")[0]["exp1"]; Console.WriteLine(resultConst); column.Expression = "iif(id not in('id1'),1000,2000)";//in运算符 resultConst = myTesttable.Select("id='id1'")[0]["exp1"]; Console.WriteLine(resultConst); column.Expression = "iif(value>5,1000,iif(id like '%1',4000,2000))"; //嵌套的三元运算 resultConst = myTesttable.Select("id='id1'")[0]["exp1"]; Console.WriteLine(resultConst); column.Expression = "value/sum(value)"; //客户端计算所占总数的百分比 resultConst = myTesttable.Select("id='id1'")[0]["exp1"]; Console.WriteLine(resultConst); column.Expression = "max(value)-value"; //客户端计算差值,比如nba常规赛的胜场差 resultConst = myTesttable.Select("id='id1'")[0]["exp1"]; Console.WriteLine(resultConst); //父子表关系 DataTable myTestTableChild = new DataTable(); myTestTableChild.Columns.Add("id", typeof(string)); myTestTableChild.Columns.Add("value", typeof(int)); DataSet myTestDataSet = new DataSet(); myTestDataSet.Tables.Add(myTestTableChild); myTestDataSet.Tables.Add(myTesttable); DataRelation relation = new DataRelation("relation", myTesttable.Columns["id"], myTestTableChild.Columns["id"]); myTestDataSet.Relations.Add(relation); for (int i = 1; i <= 10; i++) { DataRow dRow = myTestTableChild.NewRow(); dRow["id"] = "id1"; dRow["value"] = i; myTestTableChild.Rows.Add(dRow); } column.Expression = "count(child(relation).value)";//计算子表记录数 resultConst = myTesttable.Select("id='id1'")[0]["exp1"]; Console.WriteLine(resultConst); column.Expression = "value/sum(child(relation).value)";//计算父子表的百分比 resultConst = myTesttable.Select("id='id1'")[0]["exp1"]; Console.WriteLine(resultConst); column.Expression = "iif(value-sum(child(relation).value)>0,0,value-sum(child(relation).value))";//计算父子表的差值 resultConst = myTesttable.Select("id='id1'")[0]["exp1"]; Console.WriteLine(resultConst); } }

代码下载：http://download.csdn.net/detail/yysyangyangyangshan/4359153