房租管理小软件（四）：对linq的使用

１.对LInq的封装如下：

    private static System.Data.Linq.Mapping.MappingSource mappingSource = new AttributeMappingSource();
         public static MyFZDataContext a = null;
         static String path = Application.StartupPath;
         public MyFZDataContext(): base(getConnstring(), mappingSource)
         {

         }

         public MyFZDataContext(bool b): base(getConnstring(), mappingSource)
         {
             this.ObjectTrackingEnabled = b;
         }

         public static string connstring = "";
         public static XmlSerialize xml = new XmlSerialize();
         public static Common.Setting set = xml.DeSerialize();

         public static string getConnstring()
         {
             String Ip = set.IP;
             string user = set.User;
             string pass = set.Password;
             string DB = set.DB;
             connstring = "Data Source=" + Ip + ";Initial Catalog=" + DB + ";Persist Security Info=True;User ID=" + user + ";Password=" + pass + "" + ";Application Name=" + "NetHotel";
             return connstring;
         }

         public static MyFZDataContext getDataContext()
         {
             if (a == null)
             {

                 a = new MyFZDataContext(false);
             }
             return a;

         }

２.在代码中使用时加入

 using System.Data.Linq;
 using System.Linq;
 using DataBase;

３.一个从数据库，得到数据的例子

 MyFZDataContext dataContext = new MyFZDataContext();
             var v1 = from t in dataContext.VIEW_LD
                      where
                      t.账号.Contains(textEdit_Search.Text) ||
                      t.手机.Contains(textEdit_Search.Text) ||
                      t.承租人.Contains(textEdit_Search.Text)
                      select t;
             DataTable dt = DataFunction.LINQToDataTable(v1);
             this.gridControl1.DataSource = dt;

４.事务的使用

 #region 增加//增加
                 MyFZDataContext dataContext = new MyFZDataContext();
                 if (dataContext.Connection != null) { dataContext.Connection.Open(); }
                 System.Data.Common.DbTransaction tran = dataContext.Connection.BeginTransaction();
                 dataContext.Transaction = tran;
                 try
                 {
                                       dataContext.SubmitChanges();

                     tran.Commit();
                     MessageBox.Show("保存成功");
                     this.Close();
                 }
                 catch (Exception ex)
                 {

                     tran.Rollback();
                     MessageBox.Show(ex.Message);
                 }
                 #endregion 

5.把得到数据转成dataTable

 public static DataTable LINQToDataTable<T>(IEnumerable<T> varlist)
         {
             DataTable dtReturn = new DataTable();

             // column names
             PropertyInfo[] oProps = null;

             if (varlist == null) return dtReturn;

             foreach (T rec in varlist)
             {
                 //// Use reflection to get property names, to create table, Only first time, others
                 //will follow
                 if (oProps == null)
                 {
                     oProps = ((Type)rec.GetType()).GetProperties();
                     foreach (PropertyInfo pi in oProps)
                     {
                         Type colType = pi.PropertyType;

                         if ((colType.IsGenericType) && (colType.GetGenericTypeDefinition()
                         == typeof(Nullable<>)))
                         {
                             colType = colType.GetGenericArguments()[];
                         }

                         dtReturn.Columns.Add(new DataColumn(pi.Name, colType));
                     }
                 }

                 DataRow dr = dtReturn.NewRow();

                 foreach (PropertyInfo pi in oProps)
                 {
                     dr[pi.Name] = pi.GetValue(rec, null) == null ? DBNull.Value : pi.GetValue
                     (rec, null);
                 }

                 dtReturn.Rows.Add(dr);
             }
             return dtReturn;
         }