How to link the elements showed in a listBox to the element selected in a combobox

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VS2010

hello
i have a form with a listBox and a comboBox, the combobox contains the subjects, and the listBox must show only the articles of that subject. i'm using an sql server db and i dont find how to show in the listBox only the articles of the subject selected in the comboBox, help me please!

        table_subjects                               table_articles
idSubject       NameSubject            idArticle      NameArticle     idSubject
   1            Subject1         /          1       ArticleOfSubject1       1    
   2            Subject2         /          2       ArticleOfSubject2       2
   3            Subject3         /          3       Article2OfSubject2      2
                 ...                                        ...

Posted 4-May-13 9:59am

Nnorss

Updated 5-May-13 14:32pm

v5

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2 solutions

Solution 1

using System.Data.SqlClient;

SqlConnection con = new SqlConnection();
DataSet ds = new DataSet();
DataTable dt = new DataTable();

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
string subject = comboBox1.SelectedText;
listBox1.Items.Clear();
for (int i = 0; i < dt.Rows.Count; i++)
{
listBox1.Items.Add(dt.Rows[i][/*subjet_column_no*/].ToString());
}
}

public DataTable subject_view()
{
try
{
con.Open();
SqlCommand command = new SqlCommand("select * from subject_table", con);
SqlDataAdapter adapter = new SqlDataAdapter();
adapter.SelectCommand = command;
adapter.Fill(ds, "subject");
adapter.Dispose();
command.Dispose();
con.Close();
}
catch (Exception ex)
{
//MessageBox.Show("Can not open connection ! ");
}
dt = ds.Tables["subject"];
return dt;
}

Posted 5-May-13 2:14am

Member 10012743

Comments

Nnorss 5-May-13 18:02pm

The listBox must show the "NameArticle" collection of the subject selected, "table_articles" is not exploited in your solution!! Thanks for help anyway!

Member 10012743 6-May-13 14:31pm

instead of :

SqlCommand command = new SqlCommand("select * from subject_table", con);

type:

SqlCommand command = new SqlCommand("select * from table_articles", con);

its would be ok.
just change the values according to your need.
just follow the format or the idea how its been performed.

if you like it use it.
better dont try to copy and paste.
First understand how it is done; so you can do this type of problems by yourself.

-Irshad

Nnorss 6-May-13 14:49pm

thank you very much Irshad! i still have a little problem, when i click another subject, the old articles stays so the list box show articlesofSubject1+articlesOfSubject2, i want that the listBox be refreshed when i change the subject in the combobox, so the listBox must show only articlesOfSubjectSelected!

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Member 10012743 · Accepted Answer · 2013-05-06T00:42:00

Solution 2

try this code:

using System.Data.SqlClient;

SqlConnection con = new SqlConnection();
DataSet ds = new DataSet();
DataTable dt = new DataTable();

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
string subject = comboBox1.SelectedText;
int idsubject= comboBox1.SelectedIndex;
dt=subject_view(idsubject);
listBox1.Items.Clear();
for (int i = 0; i < dt.Rows.Count; i++)
{
listBox1.Items.Add(dt.Rows[i]["NameArticle"].ToString());
}
}

public DataTable subject_view(int idsubject)
{
try
{
con.Open();
SqlCommand command = new SqlCommand("select * from subject_table where idSubject ="+idsubject, con);
SqlDataAdapter adapter = new SqlDataAdapter();
adapter.SelectCommand = command;
adapter.Fill(ds, "subject");
adapter.Dispose();
command.Dispose();
con.Close();
}
catch (Exception ex)
{
//MessageBox.Show("Can not open connection ! ");
}
dt = ds.Tables["subject"];
return dt;

Posted 6-May-13 0:42am

Member 10012743

Updated 6-May-13 0:46am

v2

Comments

Nnorss 6-May-13 9:39am

Infinite thanks!! i still have a little problem, when i click another subject, the old articles stays so the list box show articlesofSubject1+articlesOfSubject2, i want that the listBox be refreshed when i change the subject in the combobox, so the listBox must show only articlesOfSubjectSelected!

Member 10012743 6-May-13 14:27pm

try to add this statement before assigning values to listBox1:

listBox1.Items.Clear();

which will clear all the data in listBox1 before assigning new values.

Nnorss 6-May-13 15:19pm

I tried this statement in several places of the code, always the same problem!

Member 10012743 7-May-13 8:39am

could you send the coding?

Nnorss 8-May-13 0:54am

here is the actual code:

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
listBox1.Items.Clear();
string theme = comboBox1.SelectedText;
int idtheme = Convert.ToInt32(comboBox1.SelectedValue);
dt = sources_view(idtheme);
for (int i = 0; i < dt.Rows.Count; i++)
{

listBox1.Items.Add(dt.Rows[i]["Url"]);
}
}

public DataTable sources_view(int idtheme)
{
try
{
myConnection.Open();
SqlCommand command = new SqlCommand("select * from Sources where IdTheme =" + idtheme, myConnection);
SqlDataAdapter adapter = new SqlDataAdapter();
adapter.SelectCommand = command;
adapter.Fill(ds, "theme");
adapter.Dispose();
command.Dispose();
myConnection.Close();

}
catch (SqlException exp)
{
MessageBox.Show(exp.Message);
}

dt = ds.Tables["theme"];
return dt;
}