if ListBox Contains, don't add

问题

I've got a Method:

FillListBox();

I call this method from different places.. But sometimes it happens, that things were loaded twice!

Now I'm trying to do something like:

if (listBox.Items[1].ToString() == "hello")
{
   DO NOT FILL
}
else
{
   FILL
}

THIS DONT WORKS! :(

Fault: InvalidArgument=Value of '1' is not valid for 'index'.
Parameter name: index

And something like that:

if(listBox.Items.Contains("hello"))
{
   DONT FILL
}

Dont works too :(

What can I do?

回答1:

Try this

if(ListBox.NoMatches != listBox.FindStringExact("StringToFind"))
  {
      listBox.Items.Add("StringToAdd");
  }

or simply try this

 bool found = false;

 foreach (var item in listBox.Items)
 {
     if(item.ToString().Equals("StringToAdd"))
     {
         found = true;
         break;
     }
 }
if(!found)
    listBox.Items.Add("StringToAdd");

回答2:

Try:

if ( listBox.Items.Cast<ListItem>().Any(x => x.Text == "hello"))

回答3:

Do this:

var item = listBox.Items.FindByValue("hello") // or FindByText
if (item != null)
{
   DONT FILL
}

回答4:

You should try something along the lines of

foreach(ListItem item in listBox)
{ 
    if(item.Value == "YourFilter")
    { 
       DONT FILL 
    }
}

if your project is ASP

you should do

foreach(object item in listBox)
{ 
    if(item == "YourFilter")
    { 
       DONT FILL 
    }
}

if it's WPF, not sure which ListBox you're talking about. Obviously this isn't the most elegant solution, but I suppose it's appropriate if you're just starting to learn C#.

回答5:

I solved the problem.. I just used myListBox.Items.Clear();

回答6:

listBox.Items.Contains("hello") should work fine.

回答7:

String newValue = "hello";
if (listBox1.Items.Cast<Object>().Any(x => x.ToString() == newValue))
{
    return;
}

来源：https://stackoverflow.com/questions/7077741/if-listbox-contains-dont-add

标签

listbox