数据库连接类

using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;
using System.Web.Configuration;
using System.Collections.Generic;

/// <summary>
///EmployeeDB 的摘要说明
/// </summary>
public class EmployeeDB
{
    private string connectionString;

    public EmployeeDB()
    {
        connectionString = WebConfigurationManager.ConnectionStrings["Northwind"].ConnectionString;

    }
    public EmployeeDB(string connectionString)
    {
        this.connectionString = connectionString;
    }
    public int InsertEmployee(EmployeeDetails emp)
    {
        SqlConnection con = new SqlConnection(connectionString);
        SqlCommand cmd = new SqlCommand("InsertEmployee", con);
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.Add(new SqlParameter("@FirstName", SqlDbType.NVarChar, 10));
        cmd.Parameters["@FirstName"].Value = emp.FirstName;
        cmd.Parameters.Add(new SqlParameter("@LastName", SqlDbType.NVarChar, 20));
        cmd.Parameters["@LastName"].Value = emp.LastName;
        cmd.Parameters.Add(new SqlParameter("@TitleOfCourtesy", SqlDbType.NVarChar, 25));
        cmd.Parameters["@TitleOfCourtesy"].Value = emp.TitleOfCourtesy;
        cmd.Parameters.Add(new SqlParameter("@EmployeeID", SqlDbType.Int, 4));
        cmd.Parameters["@EmployeeID"].Direction = ParameterDirection.Output;

        try
        {
            con.Open();
            cmd.ExecuteNonQuery();
            return (int)cmd.Parameters["@EmployeeID"].Value;
        }
        catch (SqlException err)
        {
            throw new ApplicationException("Data err.");
        }
        finally
        {
            con.Close();
        }
    }

    public void DeleteEmployee(int employeeID)
    {
        SqlConnection con = new SqlConnection(connectionString);
        SqlCommand cmd = new SqlCommand("DeleteEmployee", con);
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.Add(new SqlParameter("@EmployeeID", SqlDbType.Int, 4));
        cmd.Parameters["@EmployeeID"].Value = employeeID;

        try
        {
            con.Open();
            cmd.ExecuteNonQuery();
        }
        catch (SqlException err)
        {
            throw new ApplicationException("Data Error.");
        }
        finally
        {
            con.Close();
        }
    }

    public void UpdateEmployee(int EmployeeID, string firstName, string lastName,string titleOfCourtesy)
    {
        SqlConnection con = new SqlConnection(connectionString);
        SqlCommand cmd = new SqlCommand("UpdateEmployee", con);
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.Add(new SqlParameter("@Firstname", SqlDbType.NVarChar, 10));
        cmd.Parameters["@FirstName"].Value = firstName;
        cmd.Parameters.Add(new SqlParameter("@TitleOfCourtesy", SqlDbType.NVarChar, 25));
        cmd.Parameters["@TitleOfCourtesy"].Value = titleOfCourtesy;
        cmd.Parameters.Add(new SqlParameter("@EmployeeID", SqlDbType.Int, 4));
        cmd.Parameters["@EmployeeID"].Value = EmployeeID;

        try
        {
            con.Open();
            cmd.ExecuteNonQuery();
        }
        catch (SqlException err)
        {
            throw new ApplicationException("Data error.");
        }
        finally
        {
            con.Close();
        }
    }
    public EmployeeDetails GetEmployee(int employeeID)
    {
        SqlConnection con = new SqlConnection(connectionString);
        SqlCommand cmd = new SqlCommand("GetEmployee", con);
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.Add(new SqlParameter("@EmployeeID", SqlDbType.Int, 4));
        cmd.Parameters["@EmployeeID"].Value = employeeID;

        try
        {
            con.Open();
            SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.SingleRow);
            if (!reader.HasRows)
                return null;
            reader.Read();
            EmployeeDetails emp = new EmployeeDetails((int)reader["EmployeeID"], (string)reader["FirstName"], (string)reader["LastName"], (string)reader["TitleOfCourtesy"]);
            reader.Close();
            return emp;
        }
        catch (SqlException err)
        {
            throw new ApplicationException("Data error.");
        }
        finally
        {
            con.Close();
        }
    }

    public List<EmployeeDetails> GetEmployees()
    {
        SqlConnection con = new SqlConnection(connectionString);
        SqlCommand cmd = new SqlCommand("GetEmployees", con);
        cmd.CommandType = CommandType.StoredProcedure;

        List<EmployeeDetails> employees = new List<EmployeeDetails>();

        try
        {
            con.Open();
            SqlDataReader reader = cmd.ExecuteReader();
            while (reader.Read())
            {
                EmployeeDetails emp = new EmployeeDetails(
                    (int)reader["EmployeeID"], (string)reader["FirstName"], (string)reader["LastName"], (string)reader["TitleOfCourtesy"]);
                employees.Add(emp);
            }
            reader.Close();
            return employees;
        }
        catch (SqlException err)
        {
            throw new ApplicationException("Data error.");
        }
        finally
        {
            con.Close();
        }
    }

    public int CountEmployees()
    {
        SqlConnection con = new SqlConnection(connectionString);
        SqlCommand cmd = new SqlCommand("CoutEmployees", con);
        cmd.CommandType = CommandType.StoredProcedure;

        try
        {
            con.Open();
            return (int)cmd.ExecuteScalar();
        }
        catch (SqlException err)
        {
            throw new ApplicationException("Data error.");
        }
        finally
        {
            con.Close();
        }
    }
}