筛选DataTable行重复

 /// <summary>
        /// 验证Datatable是否已经实例
        /// </summary>
        /// <param name="dt"></param>
        /// <returns></returns>
        private bool Checkdt(DataTable dt)
        {
            if (dt == null)
            {
                MessageBox.Show("参数Datatable未实例化");
                return false;
            }
            else
                return true;
        }
        /// <summary>
        /// 验证传入筛选列是否属于欲筛选Datatable
        /// </summary>
        /// <param name="dt"></param>
        /// <param name="fieldname"></param>
        /// <returns></returns>
        private bool Checkfieldname(DataTable dt,string[] fieldname)
        {
            int flag=0;
            for (int i = 0; i < fieldname.Length; i++)
            {
                string  strfieldname = fieldname[i];
                for (int j= 0; j < dt.Columns.Count; j++)
                {
                    string colname = dt.Columns[j].ColumnName;
                    if (strfieldname == colname)
                        flag++;
                }
            }
            if (flag == fieldname.Length)
            {
                return true;
            }
            else
            {
                MessageBox.Show("存在不属于参数Datatable的列");
                return false;
            }
        }
        /// <summary>
        /// fieldname的传入顺序会影响结果
        /// 如果dt有主键可以传入主键用来筛选
        /// 出dt中不同记录
        /// </summary>
        /// <param name="dt"></param>
        /// <param name="fieldname"></param>
        /// <returns></returns>
        private DataTable dtfiter(DataTable dt,string[] fieldname)
        {
            if (Checkdt(dt) && Checkfieldname(dt,fieldname))
            {
                for (int k = 0; k < fieldname.Length; k++)
                {
                    for (int i = 0; i < dt.Rows.Count; i++)
                    {
                        string dti = dt.Rows[i][fieldname[k]].ToString();
                        for (int j = 0; j < dt.Rows.Count; j++)
                        {
                            string dtj = dt.Rows[j][fieldname[k]].ToString();
                            if (dti == dtj)
                                if (i != j && dti != string.Empty)
                                {
                                    dt.Rows.Remove(dt.Rows[j]);
                                }
                        }
                    }
                }
            }
            return dt;
        }
        private DataTable DifDatatable(DataTable dt)
        {
            List<int> samerow=new List<int>();
            int flag = 0;
            List<DataRow> listdr = new List<DataRow>();
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                DataRow dr = dt.Rows[i];
                for (int j = i+1; j < dt.Rows.Count; j++)
                {
                    DataRow secdr = dt.Rows[j];
                    for (int k = 0; k < dt.Columns.Count; k++)
                    {
                        if (dr[k].ToString() == secdr[k].ToString())
                            flag++;
                        if (flag == dt.Columns.Count)
                            samerow.Add(j);
                    }
                    flag = 0;
                }
            }
            IEnumerable<int> sameindex = samerow.Distinct();
            foreach (var item in sameindex)
            {
                listdr.Add(dt.Rows[item]);//记录dt中重复行
            }
            foreach (var item in listdr)
            {
                dt.Rows.Remove(item);//移除dt中重复行
            }
            return dt;
        }