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()[0];
                        }

                        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;
        }