两个datatable的不同字段合并成同一个datatable

DataTable dt3 = dtb.Clone();
            for (int i = 0; i < dta.Columns.Count; i++)
            {
                dt3.Columns.Add(dta.Columns[i].ColumnName);
            }
            object[] obj = new object[dt3.Columns.Count];

            for (int i = 0; i < dtb.Rows.Count; i++)
            {
                dtb.Rows[i].ItemArray.CopyTo(obj, 0);
                dt3.Rows.Add(obj);
            }

            if (dtb.Rows.Count >= dta.Rows.Count)
            {
                for (int i = 0; i < dta.Rows.Count; i++)
                {
                    for (int j = 0; j < dta.Columns.Count; j++)
                    {
                        dt3.Rows[i][j + dtb.Columns.Count] = dta.Rows[i][j].ToString();
                    }
                }
            }
            else
            {
                DataRow dr3;
                for (int i = 0; i < dta.Rows.Count - dtb.Rows.Count; i++)
                {
                    dr3 = dt3.NewRow();
                    dt3.Rows.Add(dr3);
                }
                for (int i = 0; i < dta.Rows.Count; i++)
                {
                    for (int j = 0; j < dta.Columns.Count; j++)
                    {
                        dt3.Rows[i][j + dtb.Columns.Count] = dta.Rows[i][j].ToString();
                    }
                }
            }
            dataGridWuPin.DataSource = dt3;