linq動態查詢

近日做幾個項目用到linq動態查詢,但微軟官方所提供的那些動態查詢機制相當複雜,   網上也有不少網友發過一些動態查詢的方案,本人覺得那些方案比較繁索,也不易理解，今提供一種易理解簡單實用的方法.

方法如下:

在中介層寫:

  public List<View_InvoiceTransferLog> GetTransferLogByCondition(DateTime? startDate,
            DateTime? endDate,int? startNum,int? endNum, InvoiceLogType logType)
        {
            int theType = (int)logType;
            IQueryable<View_InvoiceTransferLog> query = from view in Context.View_InvoiceTransferLogs
                                                        where
                                                        (startDate == null || view.LogDate >= startDate) &&
                                                        (endDate == null || view.LogDate <= endDate) &&
                                                        (startNum == null || view.InvoiceStartNum >= startNum) &&
                                                        (endNum == null || view.InvoiceEndNum <= endNum) &&
                                                        view.TransferType == theType
                                                        select view;
            return query.ToList();
        }

調用過程如下:

 在ui層寫

        protected void SearchButton_Click(object sender, EventArgs e)
        {
            if (!HaveCondition())
            {
                GetAllDataByStatus();
                return;
            }
            DateTime? startDate = null;
            DateTime? endDate = null;
            int? startNumber = null;
            int? endNumber = null;

            if (!ValidateData())
            {
                return;
            }
           
            //get select condition
            //
            if (!string.IsNullOrEmpty(StartDate.Text.Trim()))
            {
                startDate = DateTime.Parse(StartDate.Text.Trim());
            }
            if (!string.IsNullOrEmpty(EndDate.Text.Trim()))
            {
                endDate = DateTime.Parse(EndDate.Text.Trim());
            }
            if (!string.IsNullOrEmpty(StartNum.Text.Trim()))
            {
                startNumber = int.Parse(StartNum.Text.Trim());
            }
            if (!string.IsNullOrEmpty(EndNum.Text.Trim()))
            {
                endNumber = int.Parse(EndNum.Text.Trim());
            }
            List<View_InvoiceTransferLog> list = _control.GetTransferLogByCondition(startDate, endDate, startNumber, endNumber,InvoiceLogTypeEnum);
            gd.DataSource = list;
            gd.DataBind();
        }

簡單實用的一種動態查詢方法,就這麼幾句即可實現.本文屬本人原創,轉載請註明出處.代碼開源.