WPF FAQ
Questions and answers in this FAQ have been collected from newsgroup posts, various mailing lists and the employees of Syncfusion.

19. ListBox

 FAQ Home
   19.1 How to make the listbox scroll down to show it's last entry when the page loads?
   19.2 How to check if an item already exists in a listbox?
   19.3 How to populate a listbox with the Column Names in a Table?
   19.4 How to add items dynamically to a ListBox using an ArrayList?
   19.5 How to move items between ListBoxes?
   19.6 How to select a specific Item in a ListBox in code?
   19.7 How can you use a ListBox control to display items with Price above a specific value in one color and the ones below that value in a different color?
   19.8 How to select all the Items from a listbox when the user selects a radio button?
   19.9 How to use a single DataReader associated with two different tables to databind two different listbox controls?
   19.10 How to clear all the items in a listbox?



19.1 How to make the listbox scroll down to show it's last entry when the page loads?


<p>
<asp:ListBox id="ListBox1" runat="server"></asp:ListBox>
</p>
<p>
<asp:Button id="buttonAdd" runat="server" Text="Add"></asp:Button>
</p>


In button Click Event

VB.NET


ListBox1.Items.Add(DateTime.Now.ToString("MMM dd, yyyy") + " " + DateTime.Now.ToString("t"))
Dim scrollScript As String
scrollScript &= "<script language='javascript'>"
scrollScript &= "document.forms[0].ListBox1.selectedIndex " & _
" = document.forms[0].ListBox1.options.length-1;"
scrollScript &= "<" & "/" & "script>"
Page.RegisterStartupScript("", scrollScript)


C#


ListBox1.Items.Add(DateTime.Now.ToString("MMM dd, yyyy") + " " + DateTime.Now.ToString("t"));
string scrollScript="" ;
scrollScript += "<script language='javascript'>";
scrollScript += "document.forms[0].ListBox1.selectedIndex = document.forms[0].ListBox1.options.length-1;";
scrollScript += "<" + "/" + "script>";
Page.RegisterStartupScript("", scrollScript);



19.2 How to check if an item already exists in a listbox?

VB.NET


Dim lstitem As ListItem = ListBox1.Items.FindByValue("<valuecheckedfor>")
If Not lstitem Is Nothing Then
Response.Write("Item Exists")
Else
Response.Write("Item Does not exist")
End If


C#


ListItem lstitem = ListBox1.Items.FindByValue("<valuecheckedfor>");
if ( lstitem !=null)
{
     Response.Write ("Does exist");
}
else
{
     Response.Write ("Does not exist");
}


You can also use FindByText instead of FindByValue.


19.3 How to populate a listbox with the Column Names in a Table?

VB.NET


'Populate the dataset
Dim dc As DataColumn
For Each dc In ds.Tables(0).Columns
     ListBox1.Items.Add(dc.ColumnName)
Next


C#


//Populate the Dataset
foreach (DataColumn dc in ds.Tables[0].Columns)
{
     ListBox1.Items.Add(dc.ColumnName);
}



19.4 How to add items dynamically to a ListBox using an ArrayList?


<asp:ListBox id="ListBox1" runat="server" AutoPostBack="True"></asp:ListBox>


VB.NET


Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
     'Put user code to initialize the page here
     If Not IsPostBack Then
          Dim arrList As New ArrayList
          arrList.Add("One")
          arrList.Add("Two")
          arrList.Add("Three")
          arrList.Add("Four")
          ListBox1.DataSource = arrList
          ListBox1.DataBind()
     End If
End Sub

Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
     Response.Write(ListBox1.SelectedItem.Text)
End Sub


C#


private void Page_Load(object sender, System.EventArgs e)
{
     // Put user code to initialize the page here
     if (!Page.IsPostBack )
     {
          ArrayList arrList = new ArrayList();
          arrList.Add("One");
          arrList.Add("Two");
          arrList.Add("Three");
          arrList.Add("Four");
          ListBox1.DataSource = arrList;
          ListBox1.DataBind();
     }
}

private void ListBox1_SelectedIndexChanged(object sender, System.EventArgs e)
{
     Response.Write (ListBox1.SelectedItem.Text );
}



19.5 How to move items between ListBoxes?


<asp:ListBox id="ListBox1" runat="server">
     <asp:ListItem Value="Faqs">Faqs</asp:ListItem>
     <asp:ListItem Value="Tips">Tips</asp:ListItem>
     <asp:ListItem Value="Tricks">Tricks</asp:ListItem>
     <asp:ListItem Value="Advanced">Advanced</asp:ListItem>
</asp:ListBox>
<asp:Button id="btnToRight" style="Z-INDEX: 101; LEFT: 112px; POSITION: absolute; TOP: 24px"
     runat="server" Text=">"></asp:Button>
<asp:ListBox id="ListBox2" style="Z-INDEX: 102; LEFT: 152px; POSITION: absolute; TOP: 16px" runat="server"></asp:ListBox>
<asp:RequiredFieldValidator id="RequiredFieldValidator1" style="Z-INDEX: 103; LEFT: 24px; POSITION: absolute; TOP: 120px"
     runat="server" ErrorMessage="Please Select Item" ControlToValidate="ListBox1"></asp:RequiredFieldValidator>


VB.NET


Private Sub btnToRight_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnToRight.Click
     If ListBox1.Items.Count = 0 Then
          Response.Write("No item to move")
     End If
     Dim itemremoved As String = ListBox1.SelectedItem.Text
     ListBox1.Items.Remove(itemremoved)
     ListBox2.Items.Add(itemremoved)
End Sub


C#


private void btnToRight_Click(object sender, System.EventArgs e)
{
     if (ListBox1.Items.Count == 0 )
     {
          Response.Write("No item to move");
     }
string itemremoved = ListBox1.SelectedItem.Text;
ListBox1.Items.Remove(itemremoved);
ListBox2.Items.Add(itemremoved);
}



19.6 How to select a specific Item in a ListBox in code?

VB.NET


ListBox1.Items.FindByValue(<Value>).Selected = true
'ListBox1.Items.FindByText(<Text>).Selected = true


C#


ListBox1.Items.FindByValue(<Value>).Selected = true;
//ListBox1.Items.FindByText(<Text>).Selected = true;



19.7 How can you use a ListBox control to display items with Price above a specific value in one color and the ones below that value in a different color?

The ListBox Web server control prevents us from assigning the style property to each item in the ListBox. This bug is confirmed by Microsoft Knowledge Base Article - 309338
So, instead use a HTML ListBox with runat=server


<SELECT id="listbox1" size="14" runat="server" >
</SELECT>


VB.NET


Dim myconnection As SqlConnection
Dim myda As SqlDataAdapter
Dim ds As DataSet
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
     myconnection = New SqlConnection("Server=localhost;uid=sa;password=;database=northwind;")
     myda = New SqlDataAdapter("Select * from Products ", myconnection)
     ds = New DataSet()
     myda.Fill(ds, "AllTables")
     dim i as Integer
     For i = 0 To ds.Tables(0).Rows.Count - 1
          listBox1.Items.Add(New ListItem(ds.Tables(0).Rows(i)("UnitPrice"), ds.Tables(0).Rows(i)("ProductID")))
          If ds.Tables(0).Rows(i)("UnitPrice") <= 25 Then
               listBox1.Items(i).Attributes.Add("style", "color:red")
          Else
               listBox1.Items(i).Attributes.Add("style", "color:green")
          End If
     Next
End Sub


C#


SqlConnection mycn;
SqlDataAdapter myda;
DataSet ds;
String strConn;
private void Page_Load(object sender, System.EventArgs e)
{
     if (!IsPostBack)
     {
          strConn="Data Source=localhost;uid=sa;pwd=;Initial Catalog=northwind";
          mycn = new SqlConnection(strConn);
          myda = new SqlDataAdapter ("Select * FROM Products ", mycn);
          ds = new DataSet();
          myda.Fill (ds,"Table");
                    
          for(int i = 0 ;i < ds.Tables[0].Rows.Count - 1;i++)
          {
               listBox1.Items.Add (new ListItem(ds.Tables[0].Rows[i]["UnitPrice"].ToString(),
               ds.Tables[0].Rows[i]["ProductID"].ToString()));
               if(Convert.ToDouble(ds.Tables[0].Rows[i]["UnitPrice"].ToString()) <= 25 )
               {
                    listBox1.Items[i].Attributes.Add("style", "color:red");
               }
               else
               {
                    listBox1.Items[i].Attributes.Add("style", "color:green");
               }
          }
     }
}



19.8 How to select all the Items from a listbox when the user selects a radio button?


<asp:listbox id="ListBox1" runat="server" selectionmode="Multiple">
     <asp:listitem value="Red">Red</asp:listitem>
     <asp:listitem value="Blue">Blue</asp:listitem>
     <asp:listitem value="Green">Green</asp:listitem>
     <asp:listitem value="White">White</asp:listitem>
</asp:listbox>
<asp:radiobutton id="RadioButton1" runat="server" groupname="selrb" text="Select All" autopostback="True"></asp:radiobutton>


VB.NET


Private Sub RadioButton1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadioButton1.CheckedChanged
      Dim lstItem As ListItem
      For Each lstItem In ListBox1.Items
           lstItem.Selected = True
      Next
End Sub



C#


foreach (ListItem lstItem in ListBox1.Items)
{
     lstItem.Selected = true;
}



19.9 How to use a single DataReader associated with two different tables to databind two different listbox controls?

VB.NET


Dim cn As SqlConnection
Dim cmd As SqlCommand
Dim dr As SqlDataReader
cn = New SqlConnection("Server=localhost;uid=sa;database=northwind;pwd=")
cmd = New SqlCommand("select * from products;select * from categories", cn)
cn.Open()
dr = cmd.ExecuteReader()
ListBox1.DataSource = dr
ListBox1.DataTextField = "productname"
ListBox1.DataBind()
dr.NextResult()
ListBox2.DataSource = dr
ListBox2.DataTextField = "categoryname"
ListBox2.DataBind()


C#


SqlConnection cn;
SqlCommand cmd;
SqlDataReader dr;
cn = new SqlConnection("Server=localhost;uid=sa;database=northwind;pwd=");
cmd= new SqlCommand ("select * from products;select * from categories", cn);
cn.Open();
dr = cmd.ExecuteReader();
ListBox1.DataSource = dr;
ListBox1.DataTextField = "productname";
ListBox1.DataBind();
dr.NextResult();
ListBox2.DataSource = dr;
ListBox2.DataTextField = "categoryname";
ListBox2.DataBind();



19.10 How to clear all the items in a listbox?

VB.NET


ListBox1.Items.Clear


C#


ListBox1.Items.Clear();


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