DataTable 行列转换 将原来的行表转化成交叉表，无对应值赋默认值，用于统计显示或报表

    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;
        }
    }