Solved

What is the best way to populate comboBox from database

Posted on 2010-08-27
12
1,210 Views
Last Modified: 2013-12-17
Hi,

what is the best way to populate comboBox from database.. the reason I
am asking is that i have more than 8 comboBoxes in one form and each
should retrieve  a lot of data (one combobox contains 50000 items) from a table and I don't want that to slow the form down.

I found this as answer on the net :
You can show the form, but disable the combos. After that, launch an async
delegate populating the combos, and enable them once the data are ready.


But I have no idea on how to do this, can you please submit a sample code...
0
Comment
Question by:dekempeneer
  • 4
  • 3
  • 3
  • +2
12 Comments
 
LVL 53

Expert Comment

by:Dhaest
Comment Utility
I don't see any reason to load such a huge combobox: 50.000 items ? I don't want to be the user that open the combobox and search for my item he/she needs ...

 I would suggest that you implement a master/detail combo box wherein the user will first select a category (master) then once a selection has been made, populate another combo box (detail) for the items for the selected category...
0
 

Author Comment

by:dekempeneer
Comment Utility
It is a list of all the contacts of everybody and they are sorted by alphabet
0
 
LVL 53

Expert Comment

by:Dhaest
Comment Utility
0
 
LVL 53

Expert Comment

by:Dhaest
Comment Utility
>> It is a list of all the contacts of everybody and they are sorted by alphabet

You can for example also use some kind of search, where the user first enters 3 or 4 characters of a name, that triggers a search a database and with this results the first 50 (or 100) will be filled into a dropdown
0
 

Author Comment

by:dekempeneer
Comment Utility
and how can I do this if I would choose this ?
0
 

Author Comment

by:dekempeneer
Comment Utility
by the way that asynchronous is for .net 2.0, is there not a better easier way in 4.0 already ? :)
0
Maximize Your Threat Intelligence Reporting

Reporting is one of the most important and least talked about aspects of a world-class threat intelligence program. Here’s how to do it right.

 
LVL 53

Expert Comment

by:Dhaest
Comment Utility
Very easily: add a textbox and a button on the screen. Behind this button, you perform a query and load the data into the combobox.

Example below for an access-database
string connString = "Microsoft.Jet.OLEDB.4.0;Data Source=C:\\bd1.mdb"; 

string SqlString = "Select top 50 LastName From Contacts Where LastName like '?*'";

using (OleDbConnection conn = new OleDbConnection(ConnString))

{

  using (OleDbCommand cmd = new OleDbCommand(SqlString, conn))

  {

    cmd.CommandType = CommandType.Text;

    cmd.Parameters.AddWithValue("LastName", txtLastName.Text);

    conn.Open();

    using (OleDbDataReader reader = cmd.ExecuteReader())

    {

      while (reader.Read())

      {

        comboBox1.Items.Add(reader["LastName"].ToString());

      }

    }



  }



}

Open in new window

0
 
LVL 16

Accepted Solution

by:
SriVaddadi earned 500 total points
Comment Utility

You might want to implement producer-consumer pattern where the producer would produce the data and consumer would consume it and populate your combo.

Here is a link which might help
http://msdn.microsoft.com/en-us/library/dd997371.aspx

NOTE: It may not be a good idea to search on text fields using "Like" operator.
0
 
LVL 16

Expert Comment

by:ToddBeaulieu
Comment Utility
I'd still be concerned about performance. I agree with dhaest on this. Most UI controls get REALLY SLOW when you add such large numbers of items. Also, the thumb would be really small with that many items. A simple filter would make it so much better. A textbox to allow the user to enter a partial name would go a long way in making it more usable. When something is entered, re-issue the query, wrap the results in a new collection and bind the combo to it.
0
 
LVL 14

Expert Comment

by:systan
Comment Utility
>>I found this as answer on the net :
>>You can show the form, but disable the combos.
Use this when your form loads
comboBox1.BeginUpdate();

>>and enable them once the data are ready.
Use this after your data is complete
comboBox1.EndUpdate();  


If you want it asynchronously;
Use
comboBox1.BeginInvoke
0
 
LVL 14

Expert Comment

by:systan
Comment Utility
OR with background worker
http://www.codeguru.com/forum/showthread.php?t=433482

OR with this for simple psudo code;
//Global Declaration

SqlDataAdapter da1 = new MySqlDataAdapter();

SqlDataAdapter da2 = new MySqlDataAdapter();

SqlDataAdapter da3 = new MySqlDataAdapter();

SqlDataAdapter da4 = new MySqlDataAdapter();

SqlDataAdapter da5 = new MySqlDataAdapter();

SqlDataAdapter da6 = new MySqlDataAdapter();

SqlDataAdapter da7 = new MySqlDataAdapter();

SqlDataAdapter da8 = new MySqlDataAdapter();





//During Form LOAD

...

string s1 = "select  f1 from t1";

da1.SelectCommand = new SqlCommand(s1, YOURsqlconnection);

string s2 = "select  f1 from t2";

da2.SelectCommand = new SqlCommand(s2, YOURsqlconnection);

string s3 = "select  f1 from t3";

da3.SelectCommand = new SqlCommand(s3, YOURsqlconnection);

string s4 = "select  f1 from t4";

da4.SelectCommand = new SqlCommand(s4, YOURsqlconnection);

string s5 = "select  f1 from t5";

da5.SelectCommand = new SqlCommand(s5, YOURsqlconnection);

string s6 = "select  f1 from t6";

da6.SelectCommand = new SqlCommand(s6, YOURsqlconnection);

string s7 = "select  f1 from t7";

da7.SelectCommand = new SqlCommand(s7, YOURsqlconnection);

string s8 = "select  f1 from t8";

da8.SelectCommand = new SqlCommand(s8, YOURsqlconnection);

...

DataTable dt1 = new DataTable();

da1.Fill (dt1);

DataTable dt2 = new DataTable();

da2.Fill (dt2);

DataTable dt3 = new DataTable();

da3.Fill (dt3);

DataTable dt4 = new DataTable();

da4.Fill (dt4);

DataTable dt5 = new DataTable();

da5.Fill (dt5);

DataTable dt6 = new DataTable();

da6.Fill (dt6);

DataTable dt7 = new DataTable();

da7.Fill (dt7);

DataTable dt8 = new DataTable();

da8.Fill (dt8);













//During Form SHOWN / or button click

comboBox1.BeginUpdate();

comboBox2.BeginUpdate();

comboBox3.BeginUpdate();

-do next down-



comboBox1.DisplayMember = "f1";

comboBox2.DisplayMember = "f1";

comboBox3.DisplayMember = "f1";

-do next down-





comboBox1.DataSource = dt1;

comboBox2.DataSource = dt2;

comboBox3.DataSource = dt3;

-do next down-





comboBox1.EndUpdate();

comboBox2.EndUpdate();

comboBox3.EndUpdate();

-do next down-





Note:

//use Datatable for SMALL memory consumption

Open in new window

0
 
LVL 14

Expert Comment

by:systan
Comment Utility
OPs,
correction; for my second comment.

for MS sql
SqlDataAdapter da1 = new SqlDataAdapter();

for mYsql
MySqlDataAdapter da1 = new MySqlDataAdapter();

for ado
OLEDBlDataAdapter da1 = new OLEDBDataAdapter();

for odbc
ODbCDataAdapter da1 = new ODbcDataAdapter();
0

Featured Post

How your wiki can always stay up-to-date

Quip doubles as a “living” wiki and a project management tool that evolves with your organization. As you finish projects in Quip, the work remains, easily accessible to all team members, new and old.
- Increase transparency
- Onboard new hires faster
- Access from mobile/offline

Join & Write a Comment

This article describes relatively difficult and non-obvious issues that are likely to arise when creating COM class in Visual Studio and deploying it by professional MSI-authoring tools. It is assumed that the reader is already familiar with the cla…
In my previous two articles we discussed Binary Serialization (http://www.experts-exchange.com/A_4362.html) and XML Serialization (http://www.experts-exchange.com/A_4425.html). In this article we will try to know more about SOAP (Simple Object Acces…
Illustrator's Shape Builder tool will let you combine shapes visually and interactively. This video shows the Mac version, but the tool works the same way in Windows. To follow along with this video, you can draw your own shapes or download the file…
This video gives you a great overview about bandwidth monitoring with SNMP and WMI with our network monitoring solution PRTG Network Monitor (https://www.paessler.com/prtg). If you're looking for how to monitor bandwidth using netflow or packet s…

771 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

Need Help in Real-Time?

Connect with top rated Experts

12 Experts available now in Live!

Get 1:1 Help Now