C# で DataTable の行と列の変換を実装する方法

protected void Page_Load(object sender, EventArgs e)
{
  if (!IsPostBack)
  {
   DataTable tt = GetCrossTable(CreateDT());
   GridView1.DataSource = tt;
   GridView1.DataBind();
  }
}
//创建DataTable
protected DataTable CreateDT()
{
  DataTable tblDatas = new DataTable("Datas");
  //数据列
  tblDatas.Columns.Add("姓名", Type.GetType("System.String"));
  tblDatas.Columns.Add("科目", Type.GetType("System.String"));
  tblDatas.Columns.Add("分数", Type.GetType("System.Int32"));
  tblDatas.Rows.Add(new object[] { "张三", "语文", 89 });
  tblDatas.Rows.Add(new object[] { "张三", "数学", 90 });
  tblDatas.Rows.Add(new object[] { "张三", "英语", 79 });
  tblDatas.Rows.Add(new object[] { "张三", "地理", 70 });
  tblDatas.Rows.Add(new object[] { "张三", "生物", 95 });
  tblDatas.Rows.Add(new object[] { "李四", "语文", 87 });
  tblDatas.Rows.Add(new object[] { "李四", "英语", 86 });
  tblDatas.Rows.Add(new object[] { "李四", "地理", 82 });
  tblDatas.Rows.Add(new object[] { "王五", "语文", 81 });
  tblDatas.Rows.Add(new object[] { "王五", "数学", 70 });
  tblDatas.Rows.Add(new object[] { "王五", "英语", 88 });
  tblDatas.Rows.Add(new object[] { "王五", "生物", 96 });
  return tblDatas;
}
/// <summary>
/// 将DataTable的第二列的值转化为列
//（即将原来的行表，转化成交叉表，没有对应值则默认"0"）
/// </summary>
/// <param name="dt">必须三列，第三列为值</param>
/// <returns></returns>
public static DataTable GetCrossTable(DataTable dt)
{
  if (dt == null || dt.Columns.Count != 3 || dt.Rows.Count == 0)
  {
   return dt;
  }
  else
  {
   DataTable result = new DataTable();
   result.Columns.Add(dt.Columns[0].ColumnName);
   DataTable dtColumns = dt.DefaultView.ToTable("dtColumns", true, dt.Columns[1].ColumnName);
   for (int i = 0; i < dtColumns.Rows.Count; i++)
   {
    string colName;
    if (dtColumns.Rows[1][0] is DateTime)
    {
     colName = Convert.ToDateTime(dtColumns.Rows[i][0]).ToString();
    }
    else
    {
     colName = dtColumns.Rows[i][0].ToString();
    }
    result.Columns.Add(colName);
    result.Columns[i + 1].DefaultValue = "0";
   }
   DataRow drNew = result.NewRow();
   drNew[0] = dt.Rows[0][0];
   string rowName = drNew[0].ToString();
   foreach (DataRow dr in dt.Rows)
   {
    string colName = dr[1].ToString();
    double dValue = Convert.ToDouble(dr[2]);
    if (dr[0].ToString().Equals(rowName, StringComparison.CurrentCultureIgnoreCase))
    {
     drNew[colName] = dValue.ToString();
    }
    else
    {
     result.Rows.Add(drNew);
     drNew = result.NewRow();
     drNew[0] = dr[0];
     rowName = drNew[0].ToString();
     drNew[colName] = dValue.ToString();
    }
   }
   result.Rows.Add(drNew);
   return result;
  }
}