C# - Combobox update on form show

Question

For the start I am using Sql Server Local DB and Linq to Sql. I have two forms Form1 and Form2. There is a comboBox in Form1 that i want to update everytime it is shown. Form2 inserts new record and Form1 is for searching the record. After inserting a record when i go back to Form1. It doesnot update the list. I have tried Shown and Activated for Form1 and onClosing event for Form2 but to no luck. Also I have tried Enter event for comboBox. Though Database is updated but comboBox is not. That is how i update my comboBox

_Namelist.Clear();
_Namelist.Add("Select a Name");
_Namelist.AddRange((from p in context.Peoples
                          select p.Name).ToList());
comboBox1.DataSource = _Namelist;

I have created a separate class to make my main form that is FORM1 to be singleton. To show Form1 i have used this

FormProvider.Form_1.Show();

In this scenario how can i update my comboBox?

Update_1

If I try to search (in Form1) the new data that i have inserted (in Form2) then it finds the record perfectly, just not updating comboBox.

Update_2

I just made a new Class

public class Database
{
    static DataContext context;

    public static List<string> getNames()
    {
        context = new DataContext();
        List<string> _names = new List<string>();

        _names.Add("Select a Name");
        _names.AddRange((from p in context.People
                                   select p.Name).ToList());

        return _names;
    }

}

Calling this function in any Event call of Form1 is doing the job. Can anyone tell me why it didn't work in the scenario i have described above in my question?

Tobias · Accepted Answer · 2014-09-08T16:21:10.140

1

I would guess that it could be related to data caching in LINQ. Did you try refreshing the DataContext or flushing after creating the new record in Form2?

edited Sep 08 '14 at 16:21

answered Sep 08 '14 at 12:08

Tobias

2,089
2
26
51

how to refresh data contex – Muneeb Mirza Sep 08 '14 at 15:53
See my updated my post, it now includes a hyperlink to the `Refresh()` method. – Tobias Sep 08 '14 at 16:22
! What should i place as OBJECT. is it the DATACONTEXT? – Muneeb Mirza Sep 08 '14 at 16:31
After the Update_1 in your post the problem does not seem to be the DataContext. You write that Form1 finds the new record then. So do I see it correctly that your method `getNames()` is just not called? Did you debug into it? If this is the problem then the solution which heathesh posted should work. – Tobias Sep 09 '14 at 11:48

score 0 · Answer 2 · answered Sep 08 '14 at 12:25

Try this, make the method to update the combo box on Form1 public, then on the close event of Form2 call the method:

So on Form1:

public void PopulateNamelistComboBox()
{
    _Namelist.Clear();
    _Namelist.Add("Select a Name");
    _Namelist.AddRange((from p in context.Peoples
                      select p.Name).ToList());
    comboBox1.DataSource = _Namelist;
}

Then on Form2 in the constructor, add the event handler to call the close event:

public Form2()
{
    Closed += Form2_Closed;
}

Then add the method on Form2:

private void Form2_Closed(object sender, EventArgs e)
{
    FormProvider.Form_1.PopulateNamelistComboBox();
}

This is not solving the problem either. Unless i restart the application. — Muneeb Mirza, Sep 08 '14 at 16:10

score 0 · Answer 3 · answered Sep 08 '14 at 12:56

0

You must Try Delegate: I am pasting URL for working project related your Scenario

https://drive.google.com/file/d/0B893d39kVeIvcGhjUG80ZG05OWc/edit?usp=sharing

answered Sep 08 '14 at 12:56

Ubiquitous Developers

3,637
6
33
78

I didn't get what were you were trying to teach me. Sorry, can you elaborate what to see exactly in your app? – Muneeb Mirza Sep 08 '14 at 16:38
Here i have attached C# project for updating gridview from another form's button w/o closing any form..just download project from link and check...even if you dont get, i could paste code here.. – Ubiquitous Developers Sep 08 '14 at 17:25

C# - Combobox update on form show

3 Answers3