Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people, just like you, are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
Solved

Implmenting Threading (in Winforms C#)- Getting Error - Cross-thread operation not valid

Posted on 2008-06-22
5
2,235 Views
Last Modified: 2008-07-03
Hi,

 

I am trying to implement Threading in my application. One of my method ia taking 2 to 3 mins time for getting data from SQL Server. So I have Implemented Threading for this.

 

But I am getting error InvalidOperation Exception -  Cross-thread operation not valid: Control 'dataGridView1' accessed from a thread other than the thread it was created on.

 

Here is my sample code.

 

public partial class frmEmployee : Form

{

public frmEmployee()

{

InitializeComponent();

}

 

protected override void OnLoad(EventArgs e)

{


base.OnLoad(e);

}

private void button1_Click(object sender, EventArgs e)

{


ThreadPool.QueueUserWorkItem(new WaitCallback(GetEmployeeData));


}

private void GetEmployeeData(Object stateInfo)

{

DataAccessLayer db = new DataAccessLayer();

System.Linq.IQueryable<Employee> emp = db.GetEmployee();

dataGridView1.DataSource = emp;


}

private void EmployeeData()

{

DataAccessLayer db = new DataAccessLayer();

System.Linq.IQueryable<Employee> emp = db.GetEmployee();

dataGridView1.DataSource = emp;

}

private void button2_Click(object sender, EventArgs e)

{

SecondMethod();

}

private static void SecondMethod()

{

MessageBox.Show("This is my second test message");

}

}

 

After clicking Button1, I clicked Button2 which display me the message "This is my second test message".

But after that I am getting, Cross-thread operation not valid.

 

Please help me with this.

 

Thanks!!!

public partial class frmEmployee : Form
 
{
 
public frmEmployee()
 
{
 
InitializeComponent();
 
}
 
 
 
protected override void OnLoad(EventArgs e)
 
{
 
 
base.OnLoad(e);
 
}
 
private void button1_Click(object sender, EventArgs e)
 
{
 
 
ThreadPool.QueueUserWorkItem(new WaitCallback(GetEmployeeData));
 
 
}
 
private void GetEmployeeData(Object stateInfo)
 
{
 
DataAccessLayer db = new DataAccessLayer();
 
System.Linq.IQueryable<Employee> emp = db.GetEmployee();
 
dataGridView1.DataSource = emp;
 
 
}
 
private void EmployeeData()
 
{
 
DataAccessLayer db = new DataAccessLayer();
 
System.Linq.IQueryable<Employee> emp = db.GetEmployee();
 
dataGridView1.DataSource = emp;
 
}
 
private void button2_Click(object sender, EventArgs e)
 
{
 
SecondMethod();
 
}
 
private static void SecondMethod()
 
{
 
MessageBox.Show("This is my second test message");
 
}
 
}

Open in new window

0
Comment
Question by:r_pat72
  • 2
  • 2
5 Comments
 
LVL 18

Expert Comment

by:philipjonathan
ID: 21840053
I think the problem is with line 42
dataGridView1.DataSource = emp;

I don't think you can data bind a datagrid on a thread other than the thread where the control was created. You might want to perform data binding inside the OnLoad override, and just refresh the data (query from data source) during GetEmployeeData().
0
 
LVL 18

Expert Comment

by:carlnorrbom
ID: 21840076
It is illegal to make cross thread calls to the UI thread as far as I know, but You should be abe to override the default behaivor using:

private void GetEmployeeData(Object stateInfo)
 {
// Disable the checking for illegal crossthread calls
Control.CheckForIllegalCrossThreadCalls = false;
// Rest of code...
 DataAccessLayer db = new DataAccessLayer();
 System.Linq.IQueryable<Employee> emp = db.GetEmployee();
 dataGridView1.DataSource = emp;
 }

Just add the extra line to all method making cross thread calls. But notice that this is NOT the best solution, it's simply disabling the checking.
/Carl.
0
 
LVL 10

Accepted Solution

by:
margajet24 earned 500 total points
ID: 21840205
       private void GetEmployeeData(Object stateInfo)
        {

            DataAccessLayer db = new DataAccessLayer();

            System.Linq.IQueryable<Employee> emp = db.GetEmployee();

            if (dataGridView1.InvokeRequired)
            {
                IAsyncResult result = dataGridView1.BeginInvoke(new MethodInvoker(delegate() { dataGridView1.DataSource = emp; }), new object[] { });

                dataGridView1.EndInvoke(result);
            }
            else
            {
                dataGridView1.DataSource = emp;
            }


        }
0
 
LVL 10

Expert Comment

by:margajet24
ID: 21840212
when updating controls on a separate thread, check first InvokeRequired because directly updating the properties of the control on another thread is not allowed.
0
 
LVL 18

Expert Comment

by:carlnorrbom
ID: 21840322
margajet24 is absolutely correct, I'm a VB guy, don't know the actual implementation i C#...
0

Featured Post

Free Tool: Postgres Monitoring System

A PHP and Perl based system to collect and display usage statistics from PostgreSQL databases.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Summary: Persistence is the capability of an application to store the state of objects and recover it when necessary. This article compares the two common types of serialization in aspects of data access, readability, and runtime cost. A ready-to…
Real-time is more about the business, not the technology. In day-to-day life, to make real-time decisions like buying or investing, business needs the latest information(e.g. Gold Rate/Stock Rate). Unlike traditional days, you need not wait for a fe…

861 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question