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   <TITLE>Select an item in a ListBox or a ComboBox from code.</TITLE>

   <META NAME="Author" CONTENT="Harold Howe">

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<H3>

Select an item in a ListBox or a ComboBox from code.

</H3>

<P>

For ComboBox and single selection ListBox controls, you select an item by assigning

a number to the <TT>ItemIndex</TT> property of the ListBox or ComboBox. Assigning a

value of zero selects the first item. Assigning -1 unselects all items.

</P>

<pre>

    <font color="navy">// single selection ListBox examples</font>

    ListBox1<b>-></b>ItemIndex <b>=</b> <font color="blue">0</font><b>;</b>   <font color="navy">// selects first item</font>

    ListBox1<b>-></b>ItemIndex <b>=</b> <font color="blue">2</font><b>;</b>   <font color="navy">// selects third item</font>

    ListBox1<b>-></b>ItemIndex<b>++</b><b>;</b>     <font color="navy">// selects next item down</font>

    ListBox1<b>-></b>ItemIndex <b>=</b> <b>-</b><font color="blue">1</font><b>;</b>  <font color="navy">// unselects all items</font>

</pre>

<P>

If you would rather select an item by specifying a string, use the

<TT>IndexOf</TT> function to return the index of a string, and then assign

that index to the <TT>ItemIndex</TT> property. Selecting the

item who's text is "Uncle Bob" would look like this:</P>

<pre>

  ListBox1<b>-></b>ItemIndex <b>=</b> ListBox1<b>-></b>Items<b>-></b>IndexOf<b>(</b><font color="blue">"Uncle Bob"</font><b>)</b><b>;</b>

</pre>

<P>

For multi-select ListBox controls, you select and unselect items by reading and writing to the

<TT>Selected</TT> property of the ListBox. The <TT>Selected</TT> property functions as an array

of <TT>bool</TT>. The index of the array corresponds to the index of an item in the ListBox.

To select an item, set its <TT>Selected</TT> index value to <TT>true</TT>. Here are some code

examples.

</P>

<pre>

    <font color="navy">// multi-selection ListBox examples.</font>

    ListBox1<b>-></b>Selected<b>[</b><font color="blue">0</font><b>]</b> <b>=</b> <b>true</b><b>;</b>  <font color="navy">// adds the first item to the selection</font>

    ListBox1<b>-></b>Selected<b>[</b><font color="blue">0</font><b>]</b> <b>=</b> <b>false</b><b>;</b> <font color="navy">// removes first item from the selection</font>



    <font color="navy">// toggles the 10th item</font>

    ListBox1<b>-></b>Selected<b>[</b><font color="blue">9</font><b>]</b> <b>=</b> <b>!</b>ListBox1<b>-></b>Selected<b>[</b><font color="blue">9</font><b>]</b>



    <font color="navy">// selects a range of items</font>

    <b>for</b> <b>(</b><b>int</b> j<b>=</b><font color="blue">10</font><b>;</b> j<b><=</b><font color="blue">19</font><b>;</b> j<b>++</b><b>)</b>

        ListBox1<b>-></b>Selected<b>[</b>j<b>]</b> <b>=</b> <b>true</b><b>;</b>

</pre>

<P>

<B>Note:</B> Reading a value from the <TT>Selected</TT> array of a multi-select ListBox tells you if an item is

currently selected. A value of true means that the item is selected, and false means that the item is not selected.

Writing to the <TT>Selected</TT> array sets the selection status of an item. Writing to the <TT>Selected</TT> array selects an item if you assign

true, and it unselects an item if you assign false. Reading or writing to one item in the ListBox does not

affect other items in the ListBox.

</P>

<P>

<B>Note:</B> Do not use the <TT>Selected</TT> array in single selection ListBox controls

</P>

<P>

<B>Note:</B> In multi-select ListBox controls, you can read the <TT>ItemIndex</TT> property to determine

which ListBox item has the input focus. However, assigning a value to <TT>ItemIndex</TT> has no effect in

multi-select ListBox controls. When you write a value to <TT>ItemIndex</TT>, the VCL sends an <TT>LB_SETCURSEL</TT>

to the ListBox control. Multi-select ListBox controls ignore this message. See the Win32 API help for more info.

</P>   



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