System.invalidoperationexception in ASP.NET C#

Question

0.00/5 (No votes)

See more:

here is my coding,

protected void Button1_Click(object sender, EventArgs e)
        {
            

            SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["aspdbConnectionString"].ToString());
            SqlCommand cmd = new SqlCommand("select * from lgtab where Username='"+usr.Value+"' and Password='"+pwd.Value+"'", con);
            SqlDataReader dr = cmd.ExecuteReader();
            if (dr.Read())
            {
                ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('Login Successfully')", true);
                usr.Value = "";
                pwd.Value = "";
            }
            else
            {
                ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('Login Failed')", true);
                usr.Value = "";
                pwd.Value = "";
            }
            con.Close();
        }

I am use local db for login page, but it can't read. Please Help Something...

What I have tried:

I try above code but its shows following exception,

An exception of type 'System.InvalidOperationException' occurred in System.Data.dll but was not handled in user code

Additional information: ExecuteReader requires an open and available Connection. The connection's current state is closed.

Posted 20-Dec-20 22:37pm

Aadhi Gobi

Updated 20-Dec-20 22:43pm

Add a Solution

1 solution

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)

Sandeep Mewara · Accepted Answer · 2020-12-20T22:44:00

Entire error is quite self explanatory.

You are using SQLReader instance to read the data but have not opened up the connection with database to do so. Would recommend you to go through ADO.NET basics and then try again.

Regarding the data communication can be read here:
Accessing data with ADO.NET[^]
MSDN: Retrieving Data Using a DataReader (ADO.NET)[^]
MSDN: DataReader Class[^]
Beginners guide to accessing SQL Server through C#[^]

Sample:

C#

using (connection)
{
    SqlCommand command = new SqlCommand("SELECT CategoryID, CategoryName FROM Categories;", connection);
    connection.Open();

    SqlDataReader reader = command.ExecuteReader();

    if (reader.HasRows)
    {
        while (reader.Read())
        {
            Console.WriteLine("{0}\t{1}", reader.GetInt32(0),
                reader.GetString(1));
        }
    }
    else
    {
        Console.WriteLine("No rows found.");
    }
    reader.Close();
}