Error Handling : Connection Property Has Not Been Initialized c#

Question

5.00/5 (2 votes)

See more:

I Need Help For This Below And I Not Under Stand How To Solve This Executereader: Connection Property Has Not Been Initialized.

C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.OleDb;

namespace WindowsFormsApplication1
{
    public partial class frmlgn : Form
    {
        OleDbCommand cmd;
        
        public frmlgn()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            
            cmd = new OleDbCommand("select * from login where id='" + textBox1.Text + "'", Class1.con);
            OleDbDataReader dr;
            dr = cmd.ExecuteReader();
            dr.Read();
            if (dr.HasRows == true)
            {
                if (dr["password"].ToString() != textBox2.Text)
                {
                    MessageBox.Show("Password Not Matched!");
                    textBox2.Focus();
                }
                else
                {
                    MessageBox.Show("successfuly login");
                    this.Close();
                    MDIParent2 mdi=new MDIParent2();
                    
                                                       

                }
                }
            else
                MessageBox.Show("Invalid User id");
            dr.Close();
        }

I used this connection string in class

C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.OleDb;

namespace WindowsFormsApplication1
{
    class Class1
    {
        public static OleDbConnection con;
        public static void Connection()
        {

           con = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source= e:\db1.mdb");
            con.Open();
        }
    }
}

Posted 22-Feb-14 12:55pm

Mohamed Ragheb

Updated 22-Feb-14 16:28pm

agent_kruger

v3

Add a Solution

Comments

Garth J Lancaster 22-Feb-14 20:16pm

Im a bit mystified about the relationship of Class1 to the rest of the code, particularly where you use it in your button1_Click() handler - especially since you don't
a) show where /how you instantiate Class1
b) in button1_Click() test that Class1.con is b1) not null, b2) open

PIEBALDconsult 22-Feb-14 20:33pm

Class1.con is static, but the Connection method is never called.

Garth J Lancaster 22-Feb-14 20:49pm

ok, ta - I thought C# classes had to have the static modifier to be such, but I defer to higher wisdom :-)

3 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

agent_kruger · Accepted Answer · 2014-02-22T16:27:00

Solution 2

sir, please check as in the code above you have made the Connection function but you haven't used it before

cmd = new OleDbCommand("select * from login where id='" + textBox1.Text + "'", Class1.con);

Posted 22-Feb-14 16:27pm

agent_kruger

PIEBALDconsult · Accepted Answer · 2014-02-22T14:55:00

There are a number of problems with your code. The main one is you never call Class1.Connection() , that's why Class1.con is null.

0) Class1 is not only poorly implemented, but doesn't offer your code anything, so you should get rid of it.
1) <SHOUTING> DO NOT STORE PLAIN-TEXT PASSWORDS !!! </SHOUTING>
2) The test of the password should occur on the database side.
3) Do not use concatenation to form the query; use a parameterized query -- it's very easy.
4) Don't test HasRows; it's needless and not all providers implement it -- just test the result of Read.
5) Don't Open the Connection until you need to use it.
6) Use Using statements.

Mohamed Ragheb · Accepted Answer · 2014-02-24T02:00:00

Hello and thank you for all the help in solving the problem in the code has been modified and is now running successfully

As shown below

C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.OleDb;

namespace WindowsFormsApplication1
{
    public partial class frmlgn : Form
    {
       OleDbCommand cmd = new OleDbCommand();
        OleDbConnection con = new OleDbConnection();
        OleDbDataReader dr;
  public frmlgn()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            con.ConnectionString = Class1.con;
                con.Open();
                cmd.Parameters.Clear();
                cmd.Connection = con;
                cmd.CommandType = CommandType.Text;
                cmd.CommandText = "select * from login where id='" + textBox1.Text + "'";
                OleDbDataReader dr;
                dr = cmd.ExecuteReader();
                dr.Read();
                if (dr.HasRows == true)
                {
                    if (dr["password"].ToString() != textBox2.Text)
                    {
                        MessageBox.Show("Password Not Matched!");
                        textBox2.Focus();
                    }
                    else
                    {
                        MessageBox.Show("successfuly login");

                       
                        
                        Form1 a = new Form1();
                        this.Hide();
                        a.Show();
                        


                    }
                }
                else
                    MessageBox.Show("Invalid User id");
                dr.Close();
            }


and connection string   Class1 

As shown below

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.OleDb;

namespace WindowsFormsApplication1
{
    class Class1
{

        internal static string con = (@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source= d:\db1.mdb");
      
        }
    }

Error Handling : Connection Property Has Not Been Initialized c#

3 solutions

Solution 2

Solution 1

Solution 3

Add your solution here

Preview 0