我正在开发一个Asp.net网站,我决定通过使用oop概念来做到这一点。调用代码时从Asp.net中的其他类中的错误
所以我的第一个想法是将我的代码(整个代码后面)封装在外部类中,然后在我的Aspx页面中调用它来执行。
我犯了一个新的类,然后我得出它从主类能够访问像按钮,标签等主类控制...
当我打电话其中包括代码的方法它给了我一个错误
“对象引用未设置为对象的实例”。
所以我想这意味着我的第二类(派生的) 无法访问我的主类对象/控制,并根据它的值运行代码。
该方法应根据DropDownList执行一些代码,但会产生此错误。
我真的很感谢你的帮助!
1的后面主类代码在(aspx页面)方法:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Data;
namespace power_CMS.Authentication
{
public partial class Permissions : System.Web.UI.Page
{
//connection string
//db name = cms
SqlConnection conn = new SqlConnection("data source=.\\sqlexpress ; initial catalog=cms ; integrated security = true");
protected void Page_Load(object sender, EventArgs e)
{
}
protected void btn_grant_Click(object sender, EventArgs e)
{ //grant permission to Members
Cms c = new Cms();
c.User_Role_Insert();
}
2-A为我aspx页面的设计者代码部分
protected global::System.Web.UI.WebControls.DropDownList drp_user;
/// <summary>
/// UserDataSource control.
/// </summary>
/// <remarks>
/// Auto-generated field.
/// To modify move field declaration from designer file to code-behind file.
3-下面的代码我的派生类,我封装我的代码吧:
namespace power_CMS
{
public class Cms :power_CMS.Authentication.Permissions
{
//sql connection
public static SqlConnection conn = new SqlConnection("data source=.\\sqlexpress ; initial catalog=*** ; integrated security = true");
public void User_Role_Insert()
{
if (drp_user.SelectedIndex == 0 && drp_permission.SelectedIndex == 0 || drp_user.SelectedIndex == 0 || drp_permission.SelectedIndex == 0)
{
//make sure that user will make a valid choise with both dropdownlists
//Invalid Choise Code
lbl_confirm.Text = "Please Make A Valid Choise !";
}
else
{
// Valid Choise Code
try
{
conn.Open();
// string str = "insert into aspnet_UsersInRoles(UserId,RoleId) values('"+c.drp_user.SelectedValue+"','"+drp_permission.SelectedValue+"')";
SqlCommand cmd = new SqlCommand("aspnet_UsersInRoles_Insert", conn);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.Add("UserId", SqlDbType.UniqueIdentifier).Value = new Guid(drp_user.SelectedValue);
cmd.Parameters.Add("RoleId", SqlDbType.UniqueIdentifier).Value = new Guid(drp_permission.SelectedValue);
cmd.ExecuteNonQuery();
conn.Close();
lbl_confirm.Text = "Permission Granted ...!";
drp_user.SelectedIndex = 0;
drp_permission.SelectedIndex = 0;
}
catch (Exception)
{
lbl_confirm.Text = "Sorry <br> This User Already Have A Permission ! ";
}
}
}
}
}
哪一行代码会产生错误? – ekad
将断点在你的代码,看看哪些对象是'null' – Shyju
如果@ekad(drp_user.SelectedIndex == 0 && drp_permission.SelectedIndex == 0 || drp_user.SelectedIndex == 0 || drp_permission.SelectedIndex == 0) ,,,这行产生错误! –