edit list in wpf

Find the item in the list with the desired ID and change the desired property for that item. There are a couple of ways you can find the item - iterating the list with a for loop, or using Linq. Personally, I think a for loop is more efficient, but a Linq statement requires less code.

for (int i = 0; i < myList.Count; i++)
{
    if (myList[i].ID == ID)
    {
        myList[i].myPropery = newValue;
        break;
    }
}

or with linq

var result = (from MyItem item in myList 
              where item.ID = ID
              select item);
result.myProperty = property;

Code provided above may need tweaking because I did it from memory. BTW, this is all very basic programming stuff. Maybe you should be more open to using google.