获取错误“对象引用未设置为对象的实例”。 [英] Getting the error "object reference not set to an instance of an object".

问题描述

我提供代码..请解决错误。等待解决方案。

Im providing the code..Please solve the error. Waiting for the solution.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;


public partial class Default_login_trial : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void btnLogin_Click(object sender, EventArgs e)
    {
         DataTable dt = new DataTable();
        SqlDataAdapter adp = new SqlDataAdapter();    
        try
        {
            SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["conStr"].ConnectionString);
            SqlCommand cmd = new SqlCommand("Login_Check_Sp", con);
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.AddWithValue("@username", txtUserName.Text.Trim());
            cmd.Parameters.AddWithValue("@pwd", txtPwd.Text.Trim());
            adp.SelectCommand = cmd;          
            adp.Fill(dt);
            cmd.Dispose();
            if (dt.Rows.Count > 0)
            {
                lblStatus.Text = "Login Successfull";
                
            }
            else
            {
                lblStatus.Text = "Wrong Username/Password";
                
            }  
        }
        catch (Exception ex)
        {
            ScriptManager.RegisterStartupScript(this, this.GetType(), "Message", "alert('Oops!! following error occured : " + ex.Message.ToString() + "');", true);
        
        }
        finally
        {
            dt.Clear();
            dt.Dispose();
            adp.Dispose();         
        }     
    }
}

推荐答案

试试这样

Try like this

protected void btnLogin_Click(object sender, EventArgs e)
  {

      DataSet ds = new DataSet();
      DataTable dt = new DataTable();
      SqlDataAdapter adp = new SqlDataAdapter();

      using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["conStr"].ConnectionString))
      {
          SqlCommand cmd = new SqlCommand("Login_Check_Sp", conn);
          cmd.Parameters.AddWithValue("@username", txtUserName.Text.Trim());
          cmd.Parameters.AddWithValue("@pwd", txtPwd.Text.Trim());

          cmd.CommandType = CommandType.StoredProcedure;

          SqlDataAdapter da = new SqlDataAdapter();
          da.SelectCommand = cmd;
          da.Fill(ds);
          dt = ds.Tables[0];

          if (dt.Rows.Count > 0)
          {
              lblStatus.Text = "Login Successfull";

          }
          else
          {
              lblStatus.Text = "Wrong Username/Password";

          }
      }



  }

如果你有错误，请尝试上面的代码。

调试a和使用断点检查你得到错误。

可能有很多原因因为连接可能没有建立。

这里有一些链接解释了如何在视觉工作室中使用断点。



http://www.tutorialspoint.com/asp.net/asp.net_debugging.htm [ ^ ]



https://www.youtube.com/watch?v=k1EQndVmlOc [ ^ ]

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