C#

private delegate void delegateUpdateTextInForm(string txt);
public void updateTextInForm(string txt)
{
    if(form.InvokeRequired) // true if calling from a different thread (not owner)
    {
        // delegate points to the "updateTextInForm" function.
        delegateUpdateTextInForm dFunc = new delegateUpdateTextInForm(updateTextInForm);

        // invoke the function from the "form" object.
        form.Invoke(dFunc , new object[] { txt });
    }
    else // calling from thread that "owns" the form
    {
        txtBox.Text = txt; // ta-dam!
    }
}

SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=northwind;Integrated Security=True");            
SqlCommand cmdSelect = new SqlCommand("select * from customers", con);            
SqlDataReader dr;            
DataTable dt = new DataTable();            
DataSet ds = new DataSet();            
con.Open();            
dr = cmdSelect.ExecuteReader();            
dt.Load(dr);            
con.Close();            
Microsoft.Reporting.WinForms.ReportDataSource rds = new Microsoft.Reporting.WinForms.ReportDataSource("Customers",dt);            
this.reportViewer2.LocalReport.DataSources.Add(rds);            this.reportViewer2.LocalReport.ReportEmbeddedResource= "ReportingServices.Report1.rdlc";           
this.reportViewer2.RefreshReport();