how to pass the lisbox selected item into another form

You can achieve this with the help of custom event handler class:-

In Form2:-

1). Define a customeventhandler event like:-

public static event System.EventHandler CustomerEventHandler;

2). Store the selected item from the listbox into a static variable like :-

Public static string strListItem=string.Empty();
strListItem=lstBox.selectedValue.ToString()

3).Then on the SelectedValueChanged event of the ListBox:-

if (CustomerEventHandler != null)
    { 
        CustomerEventHandler(sender, e);

	//firing if any change made 
    }

In Form1:-

1).add the is code on the page load:-

//During this operation, bind the Form1 event with a method 
    //which will fire from Form2

    frmCustomer c = new frmCustomer();
    c.CustomerEventHandler += new EventHandler(ShowListItemInGrid);
                        //This is the method which will fire upon any change

2). Define the method bind to custom event handler in this way:-

private void ShowListItemInGrid(object sender,eventargs e)
{
....
...
//your code here for searching the selected item from the listbox
}

Please refer this link if you face some problem in this code:-
http://www.codeproject.com/Articles/34454/Pass-Data-from-One-Form-to-Another-Form[^]

Creating advanced C# custom events[^]

Please don't forget to mark this as your answer if it helps you out.

Thanks

Hi, send the selected value using query string or save value in Session or in Cache. redirect to another form and access value from Session or Cache or QueryString. and based on that show data in gridview.