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