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Demonstrates the ListSizeValidator

The ListSizeValidator evaluates a listbox or dropdownlist to determine if has enough elements listed. It is used when the user interface allows adding and removing elements to a list.

Specify the ListBox to evaluate with the ControlIDToEvaluate property.

By default, it requires at least one item in the list. Set a different minimum with the Minimum property and introduce a maximum with the Maximum property.

The ErrorMessage and SummaryErrorMessage properties support several tokens:

"{MINIMUM}" – The value of the Minimum property.
"{MAXIMUM}" – The value of the Maximum property.
"{COUNT}" – The number of items in the list.
"{COUNT:singular:plural}" – Shows either the word in the “singular” position or “plural” position based on the count. Singular is shown if the count is 1.

Controls

ListBox 1 allows a maximum of 4.
ListBox 2 allows between 2 and 3.

Listbox 1 Errors: Maximum of 4. You have 3 items.
ListBox 2 Errors:Between 2 and 3. You have 3 items.

Source Code (C#)

<script runat="server">
   protected void Button1_Click(object sender, EventArgs e)
   {
      if (PeterBlum.DES.Globals.WebFormDirector.IsValid)
      {
         // save your data here
      }
   }
   protected void MoveAtoB_Click(object sender, EventArgs e)
   {
      Transfer(ListBoxA, ListBoxB);
   }
   protected void MoveBtoA_Click(object sender, EventArgs e)
   {
      Transfer(ListBoxB, ListBoxA);
   }
   protected void Transfer(ListBox pSourceList, ListBox pDestList)
   {
      if (pSourceList.SelectedItem != null)
      {
         ListItem vItem = pSourceList.SelectedItem;
         vItem.Selected = false;
         pDestList.Items.Add(vItem);
         pSourceList.Items.Remove(vItem);
      }
   }
   
</script>

ListBox 1 allows a maximum of 4.<br/>
ListBox 2 allows between 2 and 3.<br/><br/>
<asp:ListBox ID="ListBoxA" runat="server" Height="100px" Width="50px">
   <asp:ListItem>1</asp:ListItem>
   <asp:ListItem>2</asp:ListItem>
   <asp:ListItem>3</asp:ListItem>
</asp:ListBox>
<asp:Button ID="MoveAtoB" runat="server" CausesValidation="False" OnClick="MoveAtoB_Click"
   Text="Move >>" />
<asp:Button ID="MoveBtoA" runat="server" CausesValidation="False" OnClick="MoveBtoA_Click"
   Text="<< Move" />
<asp:ListBox ID="ListBoxB" runat="server" Height="100px" Width="50px">
   <asp:ListItem>4</asp:ListItem>
   <asp:ListItem>5</asp:ListItem>
   <asp:ListItem>6</asp:ListItem>
</asp:ListBox>
<br/>
Listbox 1 Errors:
<des:ListSizeValidator ID="ListSizeValidator1" runat="server" ControlIDToEvaluate="ListBoxA"
   ErrorMessage="Maximum of {MAXIMUM}. You have {COUNT} {COUNT:item:items}." Maximum="4"
   Minimum="0">
   <ErrorFormatterContainer>
      <des:TextErrorFormatter/>
   </ErrorFormatterContainer>
</des:ListSizeValidator>
<br/>
ListBox 2 Errors:<des:ListSizeValidator ID="Listsizevalidator2" runat="server" ControlIDToEvaluate="ListBoxB"
   ErrorMessage="Between {MINIMUM} and {MAXIMUM}. You have {COUNT} {COUNT:item:items}."
   Maximum="3" Minimum="2">
   <ErrorFormatterContainer>
      <des:TextErrorFormatter/>
   </ErrorFormatterContainer>
</des:ListSizeValidator>
<br/>
<des:Button ID="Button1" runat="server" Text="Submit" OnClick="Button1_Click"></des:Button>

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