去除DataTable中重复字段

    #region  去除datatable中重复字段
        /// <summary>
        /// </summary>
        /// <param name="SourceTable"></param>
        /// <param name="FieldNames"></param>
        /// <returns></returns>
        protected DataTable SelectDistinct(DataTable SourceTable, params string[] FieldNames)
        {
            object[] lastValues;
            DataTable newTable;
            DataRow[] orderedRows;

            //if (FieldNames == null || FieldNames.Length == 0)
            //    throw new ArgumentNullException("FieldNames");

            //如果FieldNames为空，则默认查询所有的列。
            if (FieldNames == null || FieldNames.Length == 0)
            {
                FieldNames = new string[SourceTable.Columns.Count];
                for (int i = 0; i < SourceTable.Columns.Count; i++)
                {
                    FieldNames[i] = SourceTable.Columns[i].ColumnName;
                }
            }
           
            lastValues = new object[FieldNames.Length];
            newTable = new DataTable();

            foreach (string fieldName in FieldNames)
                newTable.Columns.Add(fieldName, SourceTable.Columns[fieldName].DataType);

            orderedRows = SourceTable.Select("", string.Join(",", FieldNames));

            foreach (DataRow row in orderedRows)
            {
                if (!fieldValuesAreEqual(lastValues, row, FieldNames))
                {
                    newTable.Rows.Add(createRowClone(row, newTable.NewRow(), FieldNames));

                    setLastValues(lastValues, row, FieldNames);
                }
            }
            return newTable;
        }
        private bool fieldValuesAreEqual(object[] lastValues, DataRow currentRow, string[] fieldNames)
        {
            bool areEqual = true;

            for (int i = 0; i < fieldNames.Length; i++)
            {
                if (lastValues[i] == null || !lastValues[i].Equals(currentRow[fieldNames[i]]))
                {
                    areEqual = false;
                    break;
                }
            }

            return areEqual;
        }
        private DataRow createRowClone(DataRow sourceRow, DataRow newRow, string[] fieldNames)
        {
            foreach (string field in fieldNames)
                newRow[field] = sourceRow[field];

            return newRow;
        }
        private void setLastValues(object[] lastValues, DataRow sourceRow, string[] fieldNames)
        {
            for (int i = 0; i < fieldNames.Length; i++)
                lastValues[i] = sourceRow[fieldNames[i]];
        }
        #endregion

---

调用如下：

               DataTable tbl = new DataTable();
                tbl.Columns.Add("Id", typeof(System.Int32));
                tbl.Columns.Add("City", typeof(System.String));
                tbl.Columns.Add("Province", typeof(System.String));

                tbl.Rows.Add(1, "武汉", "湖北");
                tbl.Rows.Add(2, "应城", "湖北");
                tbl.Rows.Add(3, "武汉", "湖北");

               // DataTable dt2 = SelectDistinct(tbl, null);
                DataTable dt2 = SelectDistinct(tbl,  "City", "Province" );
                //DataTable dt2 = SelectDistinct(tbl, new string[] { "City", "Province" });
                this.dataGridView1.DataSource = dt2;