Build a three-tier General DAL Class Based on Linq

Using System;
Using System. Collections. Generic;
Using System. Linq;
Using System. Text;
Using System. Data;
Using System. Data. Linq;
Using Models;

Namespace DAL
{
Public class CommandDAL <T> where T: class
{
Public DataProjectDataContext db;

Public CommandDAL ()
{
// Each user generates an independent TestClassDataContext object
// Int count = HttpContext. Current. Session. Count;
// If (HttpContext. Current. Session ["Datas"] = null)
//{
Db = new DataProjectDataContext (System. Configuration. ConfigurationManager. ConnectionStrings ["Constr"]. ConnectionString );
// HttpContext. Current. Session ["Datas"] = db;
//}
// Else
//{
// Db = HttpContext. Current. Session ["Datas"] as JCPPSContext;
//}
}

/// <Summary>
/// Insert a piece of data into the database
/// </Summary>
/// <Param name = "obj"> data to be inserted </param>
/// <Returns> </returns>
Public T Insert (T obj)
{
Try
{

Db. GetTable <T> (). InsertOnSubmit (obj );
Db. SubmitChanges ();
}
Catch (Exception ex)
{

Throw new Exception (ex. Message );
}
Return obj;
}

/// <Summary>
/// Insert multiple data entries into the database
/// </Summary>
/// <Param name = "TEntities"> set of data to be inserted </param>
Public void InsertAll (IEnumerable <T> TEntities)
{
Try'
{
Db. GetTable <T> (). InsertAllOnSubmit (TEntities );
Db. SubmitChanges ();
}
Catch (Exception ex)
{

Throw new Exception (ex. Message );
}

}

/// <Summary>
/// Modify a piece of data based on the queried data
/// </Summary>
/// <Param name = "obj"> object to be modified </param>
/// <Param name = "action"> assign values to the object to be modified by expression </param>
Public void Update (T obj, Action <T> action)
{
Try
{
Action (obj );
Db. SubmitChanges ();
}
Catch (Exception ex)
{

Throw new Exception (ex. Message );
}
}

/// <Summary>
///????
/// </Summary>
/// <Param name = "obj"> </param>
Public void Update (T obj)
{
Try
{
Db. SubmitChanges ();
}
Catch (Exception ex)
{

Throw new Exception (ex. Message );
}
}

/// <Summary>
/// Find the desired data
/// </Summary>
/// <Param name = "s"> Search Condition expression </param>
/// <Returns> returns a group of object classes </returns>
Public List <T> Select (System. Linq. Expressions. Expression <Func <T, bool> expression)
{
Try
{
Return db. GetTable <T> (). Where <T> (expression). ToList ();
}
Catch (Exception ex)
{

Throw new Exception (ex. Message );
}
}

///// <Summary>
//// Find the desired data
///// </Summary>
///// <Param name = "s"> Search Condition expression </param>
///// <Returns> returns a group of entity classes </returns>
// Public List <T> Select (System. linq. expressions. expression <Func <T, bool> expression, System. linq. expressions. expression <Func <T, bool> expression1, bool bol)
//{
// Try
//{
// Return db. GetTable <T> (). Where <T> (expression). OrderBy (expression1). ToList ();
//}
// Catch (Exception ex)
//{

// Throw new Exception (ex. Message );
//}
//}

/// <Summary>
/// Locate the desired data and perform paging search
/// </Summary>
/// <Param name = "expression"> query condition </param>
/// <Param name = "pageindex"> current page, the first page starts from 0 </param>
/// <Param name = "pagesize"> data displayed on each page </param>
/// <Param name = "count"> total number of records </param>
/// <Returns> </returns>
Public List <T> Select (System. Linq. Expressions. Expression <Func <T, bool> expression, int pageindex, int pagesize, ref int count)
{
Try
{
Count = db. GetTable <T> (). Where <T> (expression). ToList (). Count ();
Return db. GetTable <T> (). Where <T> (expression). Skip (pageindex * pagesize). Take (pagesize). ToList ();
}
Catch (Exception ex)
{

Throw new Exception (ex. Message );
}
}

/// <Summary>
/// Find all the data
/// </Summary>
/// <Param name = "s"> data type to be searched </param>
/// <Returns> returns a group of object classes </returns>
Public List <T> SelectAll (int pageindex, int pagesize, ref int count)
{
Try
{
Count = db. GetTable <T> (). ToList (). Count ();
Return db. GetTable <T> (). Skip (pageindex * pagesize). Take (pagesize). ToList ();
}
Catch (Exception ex)
{

Throw new Exception (ex. Message );
}
}

/// <Summary>
/// Find all the data
/// </Summary>
/// <Param name = "s"> data type to be searched </param>
/// <Returns> returns a group of object classes </returns>
Public List <T> SelectAll ()
{
Try
{
Return db. GetTable <T> (). ToList ();
}
Catch (Exception ex)
{

Throw new Exception (ex. Message );
}
}

/// <Summary>
/// Search for a piece of data based on the Condition
/// </Summary>
/// <Param name = "s"> Search Condition expression </param>
/// <Returns> returns an object class </returns>
Public T SelectSingle (System. Linq. Expressions. Expression <Func <T, bool> expression)
{
Try
{
Return db. GetTable <T> (). Where <T> (expression). FirstOrDefault ();
}
Catch (Exception ex)
{

Throw new Exception (ex. Message );
}
}

/// <Summary>
/// Delete a piece of data from the database
/// </Summary>
/// <Param name = "obj"> data to be deleted </param>
Public void Delete (T obj)
{
Try
{
Db. GetTable <T> (). DeleteOnSubmit (obj );
Db. SubmitChanges ();
}
Catch (Exception ex)
{

Throw new Exception (ex. Message );
}
}

/// <Summary>
/// Delete the Qualified Data
/// </Summary>
/// <Param name = "expression"> deletion condition </param>
Public void Delete (System. Linq. Expressions. Expression <Func <T, bool> expression)
{
Try
{
Db. GetTable <T> (). DeleteAllOnSubmit <T> (Select (expression ));
Db. SubmitChanges ();
}
Catch (Exception ex)
{

Throw new Exception (ex. Message );
}
}

/// <Summary>
/// Perform Batch deletion or modification based on SQL statements, which improves the efficiency of batch deletion (update ).
/// </Summary>
/// <Param name = "SQL"> SQL statement to be deleted (updated) </param>
Public void DeleteOrUpdate (String SQL)
{
Try
{
Db. ExecuteCommand (SQL );
Db. SubmitChanges ();
}
Catch (Exception ex)
{

Throw new Exception (ex. Message );
}
}
}
}