public static class ListBoxExtension
{
public static bool MoveSelectedItems(this ListBox listBox, bool isUp, Action noSelectAction)
{
if (listBox.SelectedItems.Count > 0)
{
return listBox.MoveSelectedItems(isUp);
}
else
{
noSelectAction();
return false;
}
}
public static bool MoveSelectedItems(this ListBox listBox, bool isUp)
{
bool result = true;
ListBox.SelectedIndexCollection indices = listBox.SelectedIndices;
if (isUp)
{
if (listBox.SelectedItems.Count > 0 && indices[0] != 0)
{
foreach (int i in indices)
{
result &= MoveSelectedItem(listBox, i, true);
}
}
}
else
{
if (listBox.SelectedItems.Count > 0 && indices[indices.Count - 1] != listBox.Items.Count - 1)
{
for (int i = indices.Count - 1; i >= 0; i--)
{
result &= MoveSelectedItem(listBox, indices[i], false);
}
}
}
return result;
}
public static bool MoveSelectedItem(this ListBox listBox, bool isUp, Action noSelectAction)
{
if (listBox.SelectedItems.Count > 0)
{
return MoveSelectedItem(listBox, listBox.SelectedIndex, isUp);
}
else
{
noSelectAction();
return false;
}
}
public static bool MoveSelectedItem(this ListBox listBox, bool isUp)
{
return MoveSelectedItem(listBox, listBox.SelectedIndex, isUp);
}
private static bool MoveSelectedItem(this ListBox listBox, int selectedIndex, bool isUp)
{
if (selectedIndex != (isUp ? 0 : listBox.Items.Count - 1))
{
object current = listBox.Items[selectedIndex];
int insertAt = selectedIndex + (isUp ? -1 : 1);
listBox.Items.RemoveAt(selectedIndex);
listBox.Items.Insert(insertAt, current);
listBox.SelectedIndex = insertAt;
return true;
}
return false;
}
}
private void btnUp_Click(object sender, EventArgs e)
{
this.listBox1.MoveSelectedItems(true, () => {
MessageBox.Show("请选择");
});
}
private void btnDown_Click(object sender, EventArgs e)
{
this.listBox1.MoveSelectedItems(false, () => {
MessageBox.Show("请选择");
});
}
