Filling a ComboBox

[haroldjclements]

Hello

 

This is a quite easy question I hope. I am programming in J# (apologise if this is not the correct forum, I am just seeing if anyone has an idea). I am trying to obtain to fields from a database and deposit them into a comboBox. I have my database setup and retrieving the data. My problem is how I get the data into the comboBox.

 

An example of the data is the database is:

NameID Name

1 Harold

2 Nick

3 Bob

4 James

 

When a name is selected the NameID is passed to the next form to retrieve more into on the person.

 

This is what I have so far.

 

<CODE>

sql = "SELECT * FROM tblPeople";

OleDbCommand oc = new OleDbCommand(sql, myConnection);

 

myConnection.Open();

OleDbDataReader dr = oc.ExecuteReader();

 

while (dr.Read())

{

comboBox1.get_Items().Add(dr.GetString(1) + " (" + dr.GetString(2) + ")");

}

myConnection.Close();

 

</CODE>

 

This adds the names to the comboBox but gives me a blank box until I pull the box down. Really I would like something like �Select Name� and give it the index of 0. I understand that I have not added any index�s in, this is because I am unsure how to.

 

Any help anyone could give me with this would be very much appreciated.

[Ontani]

I don't know anything about J# but i can tell if you do this in VB.NET

 

its the value you give to the combobox the value that shows until its pulled down

 

ComboBox1.Text = "Select Name"

[haroldjclements]

I don't know anything about J# but i can tell if you do this in VB.NET

 

its the value you give to the combobox the value that shows until its pulled down

 

ComboBox1.Text = "Select Name"

 

Cheers, it's

comboBox1.set_Test = "Select Name";

 

Now how do tell the comboBox the value that the name represents (the db's unique ID).

 

Thanks again,

Harold

[Ontani]

in VB.NET its something like this:

 

Dim index As Integer
index = ComboBox1.SelectedIndex

[RobEmDee]

haroldjclements:

 

Have you considered putting the data into a DataTable and then binding the ComboBox to it? In my opinion, it is a lot easier to work with underlying data through a bound control when you do so. I'll give you a quick example using C#:

 

// DataTable tblData has been filled with data from db

// Add generic row
DataRow row = tblData.NewRow();
row["Name"] = "Select Name";
row["ID"] = -1;
tblData.Rows.Add(row);

// Sort so that generic row is always first in table
tblData.DefaultView.Sort = "ID ASC";

// Bind ComboBox1
this.ComboBox1.DataSource = tblData;
this.ComboBox1.DisplayMember = "Name";
this.ComboBox1.ValueMember = "ID";

// Select generic row in ComboBox1
this.ComboBox1.SelectedValue = -1;



// You can now retrieve the bound data from the ComboBox a few different ways

// Get selected value - what you set for ComboBox1.ValueMember
int selID = (int) this.ComboBox1.SelectedValue;

// Get selected text - what you set for ComboBox1.DisplayMember
string selText = this.ComboBox1.SelectedText;

// Get selected row - the whole corresponding DataRow in the DataTable for the selected item.
DataRowView rowSel = (DataRowView) this.ComboBox1.SelectedItem;
int selID = (int) rowSel["ID"];
string selName = rowSel["Name"].ToString();

[donnacha]

You can add the data directly to the combobox using the ".add", it is basically a collection and then you can use it away.

 

But as suggested above, putting it in a dataset may help in the long run as it may also be worth storing this info in you database to allow for updates without having to change your code...

[haroldjclements]

Thanks

 

Thanks guys for all you answers their very much appreciated.

[haroldjclements]

Ok, this piece of code works fine for me. What I want to be able to do is add a value (obtained from the database) to each line of the comboBox so that if the data is saved only the �ID� is saved and not the string description.

 

I am struggling with the .NET syntax as much as anything and using J# is even harder as the volume of resource�s are very limited.

 

Thanks in advance,

Harold Clements

 

 

sql = "SELECT * FROM tblComponentType";
OleDbCommand oc = new OleDbCommand(sql, myConnection);

myConnection.Open();	
OleDbDataReader dr = oc.ExecuteReader();
		
while (dr.Read())
{
   comboBox1.get_Items().Add(dr.GetString(1) + " (" + dr.GetString(2) + ")");
}
myConnection.Close();

[RobEmDee]

haroldjclements:

I tried out J#...below is an excerpt of my code...hope it helps.

 

private DataTable tblData;

public Form1()
{
        //
        // Required for Windows Form Designer support
        //
        InitializeComponent();

        // Bind combo box
        this.BindData();
}

private void BindData()
{
        // Initialize form level DataTable
        this.tblData = new DataTable();
        this.tblData.get_Columns().AddRange(new DataColumn[]{new DataColumn("ID"), new DataColumn("Name")});

        // Create some test data (you could replace this with DataReader or DataAdapter
        for(int count = 0; count <= 10; count++)
        {
                 DataRow row = tblData.NewRow();
                 row.set_Item("ID", System.Convert.ToString(count));
                 row.set_Item("Name", "Item_" + System.Convert.ToString(count));
                 tblData.get_Rows().Add(row);
        }

        
        // Bind comboBox1 to data source
        this.comboBox1.set_DataSource(tblData);
        this.comboBox1.set_ValueMember("ID");
        this.comboBox1.set_DisplayMember("Name");

        // Register comboBox1 event
        this.comboBox1.add_SelectedIndexChanged( new System.EventHandler(this.comboBox1_SelectedIndexChanged) );
}

private void comboBox1_SelectedIndexChanged (Object sender, System.EventArgs e)
{
        // Retrieve selected row from comboBox1
        DataRowView row;
        row = (DataRowView) this.comboBox1.get_SelectedItem();

        // View the desired data - at this point you can do whatever you want with the data from the underlying DataRow
        MessageBox.Show("Selected ID: " + row.get_Item("ID").toString() + "\n Selected Text: " + row.get_Item("Name").toString());

        row = null;
}

 

My code is probably not as optimal as possible.....I have never used J# and I don't fully understand the management of type conversions in the language.

 

You are right about the online J# documentation...pretty thin. MS is in the process of adding J# examples to the QuickStarts .

[haroldjclements]

That is excellent, it works beautifully.

 

Thanks everyone :D