Invalidoperationexception error in C#

Question

1.00/5 (3 votes)

See more:

InvalidOperationException error in C#

My code:

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;

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

            String strConnString = ConfigurationManager.ConnectionStrings["conString"].ConnectionString;

            SqlConnection con = new SqlConnection(strConnString);

            con.Open();

            SqlCommand cmd = new SqlCommand("select * from Expense_Type");

            DropDownListexpensetype.DataSource = cmd.ExecuteReader();
            DropDownListexpensetype.DataTextField = "Expense_Type";
            DropDownListexpensetype.DataValueField = "Expense_Type";
            DropDownListexpensetype.DataBind();
       


        }

        protected void BtncreateExpense_Click(object sender, EventArgs e)
        {
           

        }

    }
}

What I have tried:

Googled it but not getting proper solution

Posted 18-Jul-18 20:58pm

Virendra S from Bangalore, Karnataka

Updated 25-Jul-18 0:12am

Add a Solution

Comments

Jochen Arndt 19-Jul-18 3:34am

Would be good to know which function call throws the execption.

It might be con.Open(). Then check your connection string.

It might be also later when using the SqlDataReader object returned by cmd.ExecuteReader(). But you did not show the code using that.

F-ES Sitecore 19-Jul-18 5:15am

Whenever you get an error always say what line the error occurs on.

4 solutions

Solution 3

Issue has been rectified.
Corrected code part is:

SqlCommand cmd = new SqlCommand("select * from Expense_Type", con);

Posted 24-Jul-18 20:05pm

Virendra S from Bangalore, Karnataka

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)

Vincent Maverick Durano · Accepted Answer · 2018-07-19T03:34:00

Just wanted to add something to what they've suggested. Here are a few points that you want to consider:

(1) When binding a Data Control manually at Page_Load event, make sure that you wrap your code for binding within !IsPostback block to avoid unexpected results.

(2) Make it a habit to put objects that eat resources such as SqlConnection, SqlCommand and SqlDataAdapter within a using statement to ensure that objects will be properly disposed and closed after they are used.

C#

protected void Page_Load(object sender, EventArgs e){
      if(!IsPostback){
	          BindList();
       }  
}


private void BindList(){
     	String strConnString = ConfigurationManager.ConnectionStrings["conString"].ConnectionString;
            using(SqlConnection con = new SqlConnection(strConnString)){
            	using(SqlCommand cmd = new SqlCommand("select * from Expense_Type", con)){
			         con.Open();
            		DropDownListexpensetype.DataSource = cmd.ExecuteReader();
            		DropDownListexpensetype.DataTextField = "Expense_Type";
            		DropDownListexpensetype.DataValueField = "Expense_Type";
            		DropDownListexpensetype.DataBind();
	    	}
	    }
}

Note: I've noticed that you've assigned the field Expense_Type for both Text and Value. Just make sure that the DataValueField contain unique values to avoid unexpected behavior when selecting/pre-selecting values from the list.

ZurdoDev · Accepted Answer · 2018-07-19T03:06:00

Solution 1

You can't get the proper solution from google because you don't know which line of code is causing that error. The error is pretty generic. AND, there is more to the error message so you need to share that too.

However, I can tell you one problem. You did not associate the SqlCommand with a connection. You can do this:

C#

SqlCommand cmd = new SqlCommand("select * from Expense_Type", con);

Posted 19-Jul-18 3:06am

ZurdoDev

Comments

Vincent Maverick Durano 19-Jul-18 9:33am

5ed. Great catch!

Virendra S from Bangalore, Karnataka 25-Jul-18 2:03am

Thnx, it worked.. corrected code is /* SqlCommand cmd = new SqlCommand("select * from Expense_Type", con); */

Chinnu2020 · Accepted Answer · 2018-07-25T00:11:00

Solution 4

SqlCommand cmd = new SqlCommand("select * from Expense_Type", con);

you have missed connection instance, Please check above line. it should work

Posted 25-Jul-18 0:11am

Chinnu2020

Comments

Richard Deeming 25-Jul-18 9:57am

As mentioned last week in solution 1.

And again earlier today in solution 3.

Invalidoperationexception error in C#

4 solutions

Solution 2

Solution 1

Solution 3

Solution 4

Add your solution here

Preview 0

Existing Members

...or Join us