DataAccess层:
using System;
using System.Text;
using System.Data.SqlClient;
using System.Data;
using System.Web;namespace DataAccess
{
/// <summary>
/// 数据库访问助手
/// <summary>
public class DbHelper
{
public DbHelper()
{
}
#region 定义连接字符串strCon
/// <summary>
/// 定义连接字符串strCon
/// </summary>
public static string strCon = "Data Source =(local);database=control_OAdb ; uid = sa;pwd =";
#endregion #region 实例化连接对象con
/// <summary>
/// 实例化连接对象con
/// </summary>
SqlConnection con = new SqlConnection(strCon);
#endregion #region 检测连接是否打开
/// <summary>
/// 检测连接的方法CheckConnection(),若连接是关闭的则打开SqlConnection连接
/// </summary>
public void CheckConnection()
{
if (this.con.State == ConnectionState.Closed)
{
this.con.Open();
}
}
#endregion #region 执行语句返回DataSet数据集
/// <summary>
/// 执行语句返回DataSet数据集
/// </summary>
/// <param name="strSQL">要执行的SQL语句</param>
/// <returns>DataSet集合</returns>
public DataSet ReturnDataSet(string strSQL)
{
CheckConnection();
try
{
SqlDataAdapter sda = new SqlDataAdapter(strSQL, con);
DataSet ds = new DataSet();
sda.Fill(ds);
return ds;
}
catch (Exception ex)
{
throw new Exception(ex.Message);
}
finally
{
con.Close();
}
}
#endregion
}
}
Bussiness层:using System;
using System.Text;
using System.Data;
using DataAccess;namespace Bussiness
{
#region 业务逻辑层
/// <summary>
/// 业务逻辑层
/// 构造SQL语句及调用方法执行
/// </summary>
#endregion public class department
{
/// <summary>
/// 实例化DbHelper类的对象,用于调用其内部方法来执行不同的操作
/// </summary>
DbHelper DH = new DbHelper();
#region 获取全部部门
/// <summary>
/// 获取全部部门内容
/// </summary>
/// <returns></returns>
public DataSet GetData_department()
{
string strSQL = "select * from department";
return DH.ReturnDataSet(strSQL);
}
#endregion}}
页面绑定代码(绑定下拉列表):
DDLdep.DataSource = dep.GetData_department();
DDLdep.DataTextField = "tag";
DDLdep.DataValueField = "tag_id";
DDLdep.DataBind();错误:未将对象引用设置到对象的实例。
说明: 执行当前 Web 请求期间,出现未处理的异常。请检查堆栈跟踪信息,以了解有关该错误以及代码中导致错误的出处的详细信息。 异常详细信息: System.NullReferenceException: 未将对象引用设置到对象的实例。行 23: /// </summary>
行 24: public static string strCon = "Data Source =(local);database=control_OAdb ; uid = sa;pwd =";
行 25: //public static string strCon = ConfigurationManager.ConnectionStrings["SqlConnStr"].ConnectionString;
行 26: #endregion
using System;
using System.Text;
using System.Data.SqlClient;
using System.Data;
using System.Web;namespace DataAccess
{
/// <summary>
/// 数据库访问助手
/// <summary>
public class DbHelper
{
public DbHelper()
{
}
#region 定义连接字符串strCon
/// <summary>
/// 定义连接字符串strCon
/// </summary>
public static string strCon = "Data Source =(local);database=control_OAdb ; uid = sa;pwd =";
#endregion #region 实例化连接对象con
/// <summary>
/// 实例化连接对象con
/// </summary>
SqlConnection con = new SqlConnection(strCon);
#endregion #region 检测连接是否打开
/// <summary>
/// 检测连接的方法CheckConnection(),若连接是关闭的则打开SqlConnection连接
/// </summary>
public void CheckConnection()
{
if (this.con.State == ConnectionState.Closed)
{
this.con.Open();
}
}
#endregion #region 执行语句返回DataSet数据集
/// <summary>
/// 执行语句返回DataSet数据集
/// </summary>
/// <param name="strSQL">要执行的SQL语句</param>
/// <returns>DataSet集合</returns>
public DataSet ReturnDataSet(string strSQL)
{
CheckConnection();
try
{
SqlDataAdapter sda = new SqlDataAdapter(strSQL, con);
DataSet ds = new DataSet();
sda.Fill(ds);
return ds;
}
catch (Exception ex)
{
throw new Exception(ex.Message);
}
finally
{
con.Close();
}
}
#endregion
}
}
Bussiness层:using System;
using System.Text;
using System.Data;
using DataAccess;namespace Bussiness
{
#region 业务逻辑层
/// <summary>
/// 业务逻辑层
/// 构造SQL语句及调用方法执行
/// </summary>
#endregion public class department
{
/// <summary>
/// 实例化DbHelper类的对象,用于调用其内部方法来执行不同的操作
/// </summary>
DbHelper DH = new DbHelper();
#region 获取全部部门
/// <summary>
/// 获取全部部门内容
/// </summary>
/// <returns></returns>
public DataSet GetData_department()
{
string strSQL = "select * from department";
return DH.ReturnDataSet(strSQL);
}
#endregion}}
页面绑定代码(绑定下拉列表):
DDLdep.DataSource = dep.GetData_department();
DDLdep.DataTextField = "tag";
DDLdep.DataValueField = "tag_id";
DDLdep.DataBind();错误:未将对象引用设置到对象的实例。
说明: 执行当前 Web 请求期间,出现未处理的异常。请检查堆栈跟踪信息,以了解有关该错误以及代码中导致错误的出处的详细信息。 异常详细信息: System.NullReferenceException: 未将对象引用设置到对象的实例。行 23: /// </summary>
行 24: public static string strCon = "Data Source =(local);database=control_OAdb ; uid = sa;pwd =";
行 25: //public static string strCon = ConfigurationManager.ConnectionStrings["SqlConnStr"].ConnectionString;
行 26: #endregion
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public static const strCon = "Data Source =(local);database=control_OAdb ; uid = sa;pwd =";
public static const string strCon = "Data Source =(local);database=control_OAdb ; uid = sa;pwd =";