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    protected void Page_Load(object sender, EventArgs e)
    {
        creatDataTable();        
    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        DataTable DataTableA = ViewState["datatable1"] as DataTable;
        DataTable DataTableB = ViewState["datatable2"] as DataTable;
        DataTableB.Columns.Add("flag", typeof(String));
        DataTableB.Columns["flag"].DefaultValue = "×";
        DataView dv1 = DataTableA.DefaultView;
        DataView dv2 = DataTableB.DefaultView;
        foreach (DataRowView drv1 in dv1)
        {
            dv2.RowFilter = " id = '" + drv1["id"].ToString() + "'";
            if (dv2.Count > 0)
            {
                if (CompareUpdate(drv1, dv2[0]))//比较是否相同
                {
                    dv2[0].Row["flag"] = "√";
                }
                else
                {
                    dv2[0].Row["flag"] = "×";
                }
            }
        }
        GridView3.DataSource = MergeDataTable(DataTableA,DataTableB);
        GridView3.DataBind();
    }

    #region 创建测试DataTable
    protected void creatDataTable()
    {
        //第一步 先初始化数据 
        DataTable dtA = new DataTable();
        dtA.Columns.Add("id", typeof(int));
        dtA.Columns.Add("name", typeof(string));
        dtA.Rows.Add(1, "a");
        dtA.Rows.Add(2, "b");
        dtA.Rows.Add(3, "c");
        dtA.Rows.Add(4, "d");

        DataTable dtB = dtA.Clone();
        dtB.Rows.Add(1, "a");
        dtB.Rows.Add(2, "d");
        dtB.Rows.Add(3, "e");
        dtB.Rows.Add(4, "f");

        GridView1.DataSource = dtA;
        GridView1.DataBind();

        GridView2.DataSource = dtB;
        GridView2.DataBind();

        ViewState["datatable1"] = dtA;
        ViewState["datatable2"] = dtB;
    }
    #endregion 

    #region 比较数据行是否相同
    /// <summary>
    /// 比较数据行是否相同
    /// </summary>
    /// <param name="dr1"></param>
    /// <param name="dr2"></param>
    /// <returns></returns>
    private static bool CompareUpdate(DataRowView dr1, DataRowView dr2)
    {
        //行里只要有一项不一样，整个行就不一样,无需比较其它
        object val1;
        object val2;
        for (int i = 1; i < dr1.Row.ItemArray.Length; i++)
        {
            val1 = dr1[i];
            val2 = dr2[i];
            if (!val1.Equals(val2))
            {
                return false;
            }
        }
        return true;
    }
    #endregion 

    #region 合并两个DataTable列
    /// <summary>
    /// 合并两个DataTable列
    /// </summary>
    /// <param name="dt1"></param>
    /// <param name="dt2"></param>
    /// <returns></returns>
    public static DataTable MergeDataTable(DataTable dt1, DataTable dt2)
    {
        //定义dt的行数 
        int dtRowCount = 0;
        //dt的行数为dt1或dt2中行数最大的行数 
        if (dt1.Rows.Count > dt2.Rows.Count)
        {
            dtRowCount = dt1.Rows.Count;
        }
        else
        {
            dtRowCount = dt2.Rows.Count;
        }
        DataTable dt = new DataTable();
        //向dt中添加dt1的列名 
        for (int i = 0; i < dt1.Columns.Count; i++)
        {
            dt.Columns.Add(dt1.Columns[i].ColumnName + "1");
        }
        //向dt中添加dt2的列名 
        for (int i = 0; i < dt2.Columns.Count; i++)
        {
            dt.Columns.Add(dt2.Columns[i].ColumnName + "2");
        }
        for (int i = 0; i < dtRowCount; i++)
        {
            DataRow row = dt.NewRow();
            for (int j = 0; j < dt.Columns.Count; j++)
            {
                for (int k = 0; k < dt1.Columns.Count; k++) { if ((dt1.Rows.Count - 1) >= i) { row[k] = dt1.Rows[i].ItemArray[k]; } }
                for (int k = 0; k < dt2.Columns.Count; k++) { if ((dt2.Rows.Count - 1) >= i) { row[dt1.Columns.Count + k] = dt2.Rows[i].ItemArray[k]; } }
            }
            dt.Rows.Add(row);
        }
        return dt;
    }
    #endregion