设置DataDirectory

采用附加mdf文件的方式连接数据库时，将MDF文件放在App_Data文件夹下

然后设置DataDirectory

            string dataDir = AppDomain.CurrentDomain.BaseDirectory;
            if (dataDir.EndsWith(@"\bin\Debug\")
                || dataDir.EndsWith(@"\bin\Release\"))
            {
                dataDir = System.IO.Directory.GetParent(dataDir).Parent.Parent.FullName;
                AppDomain.CurrentDomain.SetData("DataDirectory", dataDir);
            }

连接字符串：

<add name="App1ConnectionString" connectionString="Data Source=.\SQLEXPRESS;
     AttachDbFilename=|DataDirectory|\App1.mdf;Integrated Security=True;User Instance=True" 
     providerName="System.Data.SqlClient"/>