怎样水平的数据从数据库转换成垂直的datagridview在C＃

Question

我有学生商标表数据库以这种形式

---------------------------------- 
|R.N| Student Name|Subjects|Marks| 
---------------------------------- 
|1 |Indra Poudel |DBMS |75 | 
|1 |Indra Poudel |SAD  |75 | 
|1 |Indra Poudel |TOC  |75 | 
|2 |Jon snow  |DBMS |75 | 
|2 |Jon snow  |SAD  |75 | 
|2 |Jon snow  |TOC  |75 | 
---------------------------------- 

现在我要显示在DataGridView在以下这些数据形式

---------------------------------- 
|R.N| Student Name|DBMS|SAD |TOC| 
---------------------------------- 
|1 |Indra Poudel |75 |75 |75 | 
|2 |Jon snow  |75 |75 |75 | 
---------------------------------- 

Answer 1

你需要一个数据透视表：

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
using System.Data; 


namespace ConsoleApplication73 
{ 
    class Program 
    { 

     static void Main(string[] args) 
     { 
      DataTable dt = new DataTable(); 

      dt.Columns.Add("R.N", typeof(int)); 
      dt.Columns.Add("Student Name", typeof(string)); 
      dt.Columns.Add("Subjects", typeof(string)); 
      dt.Columns.Add("Marks", typeof(int)); 

      dt.Rows.Add(new object[] { 1, "Indra Poudel", "DBMS", 75 }); 
      dt.Rows.Add(new object[] { 1, "Indra Poudel", "SAD", 75 }); 
      dt.Rows.Add(new object[] { 1, "Indra Poudel", "TOC", 75 }); 
      dt.Rows.Add(new object[] { 2, "John show", "DBMS", 75 }); 
      dt.Rows.Add(new object[] { 2, "John show", "SAD", 75 }); 
      dt.Rows.Add(new object[] { 2, "John show", "TOC", 75 }); 

      string[] subjects = dt.AsEnumerable().Select(x => x.Field<string>("Subjects")).Distinct().ToArray(); 

      DataTable pivot = new DataTable(); 
      pivot.Columns.Add("R.N", typeof(int)); 
      pivot.Columns.Add("Student Name", typeof(string)); 

      foreach (string subject in subjects) 
      { 
       pivot.Columns.Add(subject, typeof(int)); 
      } 

      var groups = dt.AsEnumerable().GroupBy(x => x.Field<int>("R.N")); 

      foreach (var group in groups) 
      { 
       DataRow newRow = pivot.Rows.Add(); 
       newRow["R.N"] = group.FirstOrDefault().Field<int>("R.N"); 
       newRow["Student Name"] = group.FirstOrDefault().Field<string>("Student Name"); 

       foreach (var col in group) 
       { 
        newRow[col.Field<string>("Subjects")] = col.Field<int>("Marks"); 
       } 

      } 


     } 
    } 


}