I have this code today:
MyListView.Items[index].Selected = true;
And I want to control that the value of index is valid. How do I check within the ListViewItemCollection if that element exists?
You would have to check if index is within the range of the collection before trying to access it if you do not wish for an IndexOutOfRangeException to be thrown.
This can be done something like this:
if (index < MyListView.Items.Count()){
MyListView.Items[index].selected = true;
} else {
// handle the index being outside the collection
}
Related
I have a problem with my code. Compiler stop on this line when I try to pick up the object.
ekwipunek.ListaNaszychPrzedmiotow[i] = BazaDanych_Eq.ListaPrzedmiotow [IdPrzedmiotu];
ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
if ( Input.GetKeyDown (KeyCode.Q))
{
IdPrzedmiotu = DoPodniesienia.GetComponent<PrzedmiotPodniesienie>().id;
for (int i = 0; i < ekwipunek.ListaNaszychPrzedmiotow.Count; i++)
{
if (ekwipunek.ListaNaszychPrzedmiotow[i].id == 0 && DoPodniesienia != null)
{
ekwipunek.ListaNaszychPrzedmiotow[i] = BazaDanych_Eq.ListaPrzedmiotow [IdPrzedmiotu];
Destroy(DoPodniesienia);
DoPodniesienia = null;
}
}
}
Your problem, more than likely, exists because one of your indices on this line references something that would be outside of the range of the collection.
You're setting this variable that is used as an index to an id.
IdPrzedmiotu = DoPodniesienia.GetComponent<PrzedmiotPodniesienie>().id;
Then, you're referencing it further down without verifying that it is available in your collection.
BazaDanych_Eq.ListaPrzedmiotow [IdPrzedmiotu]
You need to validate this value or this collection before accessing it.
Future Debugging Tip: ArgumentOutOfRangeException
Check the count of any collection you are using
Check the value of any index you will use to reference the collection
public class YourClass
{
...
Debug.Log($"The collection \"ListaNaszychPrzedmiotow\" is {ListaNaszychPrzedmiotow.Count()}");
Debug.Log($"The index value of \"i\" is {i}");
...
}
I'm constantly getting the same error.
An unhandled exception of type 'System.ArgumentOutOfRangeException' occurred in System.Windows.Forms.dll
Additional information: InvalidArgument=Value of '0' is not valid for 'index'.
The Code is:
private void radGridView1_CellFormatting(object sender, Telerik.WinControls.UI.CellFormattingEventArgs e)
{
if (e.CellElement.ColumnInfo.HeaderText == "logo")
{
if (e.CellElement.RowInfo.Cells[2].Value.ToString() == "Error")
{
e.CellElement.Image = (Image)imageList1.Images[0];
e.CellElement.ToolTipText = "Error";
}
else if (e.CellElement.RowInfo.Cells[2].Value.ToString() == "Warning")
{
e.CellElement.Image = imageList1.Images[1];
e.CellElement.ToolTipText = "Warning";
}
else if (e.CellElement.RowInfo.Cells[2].Value.ToString() == "Message")
{
e.CellElement.Image = imageList1.Images[2];
e.CellElement.ToolTipText = "Message";
}
}
}
}
//-----------------------------------------------------------------------
MSDN says this
The exception that is thrown when the value of an argument is outside the allowable range of values as defined by the invoked method.
about the ArgumentOutOfRangeException. It goes on to say that
You are retrieving the member of a collection by its index number, and the index number is invalid.
This is the most common cause of an ArgumentOutOfRangeException
exception. Typically, the index number is invalid for one of three
reasons:
The collection has no members, and your code assumes that it does.
You're attempting to retrieve an item whose index is negative. This
usually occurs because you've searched a collection for the index of a
particular element and have erroneously assumed that the search is
successful.
You're attempting to retrieve an element whose index is equal to the
value of the collection's Count property.
My suspicion is that it's the first case here, i.e. imageList1 is empty. So your imageList1.Images[0] throws the exception because there is nothing there.
To determine if this is the case try imageList1.Images.Count. Given you're looking at 3 elements in your code Count must be >= 3.
From the looks of it, you don't have anything in the array. Do a check to see if the indices are actually initialized, and then go on from there.
I am trying to implement solution for problem explined on http://users.metropolia.fi/~dangm/blog/?p=67.
I am new to c# language.I want to iterate through the dictionary using enumerator and for a particular condition.So there are two variables current and previous.current points to first element of dictionary.previous points to previous element in dictionary.While iterating over dictionary I am iterating like foll
previous=current;
current.MoveNext();
The problem is when we iterate first time thru whole dictionary previous points to last element in dictionary and current points to random keyvalue pair RawVariable(0,0).But now for when we iterate second time through dictionary i want current to point to first element in dictionary.how do i make current point to some element that has a particular key or value
Here is my code snippet
public void falling_disks(int[] A, int[] B)
{
Dictionary<int, int> filledDictionary = filldictionary(d1, A);
//previous stores the previous element in dictionary
var previous = filledDictionary .GetEnumerator();
//current stores next element of previous
var current = filledDictionary .GetEnumerator();
current.MoveNext();
//for each incoming element in array B
foreach (int ele in B)
{
//check if the current key is filled in hashtable h1 that is check if it
//is already added
if (!checkifthatvalueisfilled(current.Current.Key))
{
//if not check if current value is less than or equal to element
while ((current.Current.Value >= ele))
{
//assign previous to current
previous = current;
//move current to next position
current.MoveNext();
}
listofitemstoremove.Add(previous.Current.Key);
}
else
{
listofitemstoremove.Add(current.Current.Key);
}
foreach (int item in listofitemstoremove)
{
if (!(h1.ContainsKey(item)))
h1.Add(item, true);
}
}
Console.WriteLine(listofitemstoremove.Capacity);
}
public bool checkifthatvalueisfilled(int key)
{
if (h1.ContainsValue(h1.ContainsKey(key)) == true)
return true;
else return false;
}
}
Your question is difficult to understand. Perhaps this is what you want to do at the beginning of your loop?
current = h1.GetEnumerator();
current.MoveNext();
If i understood your question correctly, you cant do it. Enumerator gives you consecutive access to the collection, that's the whole point. You cant suddenly move it to the particular element, without iterating to that element from the beginning.
Futheremore i dont see a single good reason to use enumerator. If you need refs to previous and current elements for your algorithm - you should store their keys, not enumerators. Also im pretty sure that these lines
while ((current.Current.Value >= ele))
{
//assign previous to current
previous = current;
//move current to next position
current.MoveNext();
}
a) will throw an exception, when you ll reach the end of the collection b) wont work as expected since you are assigning reference types
I'm not sure that I understand your question, but perhaps you want to change this:
previous = current;
To this:
previous.MoveNext();
That way 'previous' will always be one step behind 'current'. If you assign the variables the way you do in the original code, you just have two references to the 'current' object which is then incremented.
I created a Listview control with 8 columns. When I need to retrieve text from subitem of Item, I use the following code:
foreach (ListViewItem item in listViewStatus.Items)
{
if (item.Tag == f)
{
/* Use locking to synchronise across mutilple thread calls. */
lock (_lockObject)
{
item.SubItems[6].Text = Status;
}
break;
}
}
it shows an exception. But when I replace item.SubItems[6].Text with item.SubItems[5].Text it works. How can I fix this?
Obviously you have at most 6 columns in SubItems
If you've only created 6, then the values are 0-5; meaning 6 is invalid.
This is a classic "off-by-one" error scenario.
Indicies come in two flavors: Zero-based, and One-based. C# is a zero-based index language. I assume you're either learning a language for the first time, or learning a zero-based language for the first time - Otherwise, I'm missing the point of the question, and I apologize. :)
See Wikipedia, Off-By-One Error: http://en.wikipedia.org/wiki/Off-by-one_error
The ArgumentOutOfRange exception is thrown by the runtime when it realizes that there is no 7th item in the list. This kind of error cannot be caught at compile time (without using heuristics), due to the fact that the list may contain any number of values at any time
TLRD;
Zero-Based (C#):
... = myList[0]; // This is a zero-based indexer.
... = myList[1];
... = myList[2];
... = myList[3];
... = myList[4];
... = myList[5]; // This is the 6th item, although the index is 5.
One-Based (some other language):
... = myList[1]; // This is a one-based indexer.
... = myList[2];
... = myList[3];
... = myList[4];
... = myList[5];
... = myList[6]; // This is the 6th item, and the index is 6.
SubItems[6]
6 there represents the column index not the index of a row.
I have below condition in my C# 2.0.
There is some VbScript code:
For i = 0 to UBound(components) - 1
If i = UBound(Components) - 1 Then
WriteOut "<div class=""clearBoth""></div>"
End If
Next
Below I am trying to write in C#, please suggest what condition will be written for "If i = UBound(Components) - 1 Then" in c#.
List<tc.ComponentPresentation> cmp = new List<tc.ComponentPresentation>();
foreach (tc.ComponentPresentation cm in cmp)
{
//Here I want to right one condition that
if(this is the last object in "cmp" list)
{
////do something
}
}
Please suggest!!
if (cmp[cmp.Count - 1] == cm)
That should work.
tc.ComponentPresentation lastItem = cmp[cmp.Count - 1];
The simplest approach would be to use the indexer instead:
for (int i = 0; i < cmp.Count; i++)
{
var cm = cmp[i];
if (i == cmp.Count - 1)
{
// Handle the last value differently
}
}
An alternative is to use something like the "smart enumerations" from MiscUtil, which lets you use a foreach loop but still access the "is first", "is last", and "index" for each entry. With C# 3 it's actually somewhat simpler to use than the code in that blog post:
foreach (var entry in SmartEnumerable.Create(cmp))
{
var cm = entry.Value;
if (entry.IsLast)
{
...
}
}
(As an aside, tc is an odd namespace name...)
EDIT: Note that checking whether your current item is equal to the last item in the list is not a reliable indication that you're currently on the last iteration. It will only work if the list contains distinct elements. Both of the approaches above really tell you whether you're on the last iteration, which is what I assumed you wanted.
Try this :
cmp[cmp.Count - 1];
Change the 'foreach' loop into a 'for' loop and use the indexer for the loop to copare to cmp.Length
Why do you need to iterate through the list?
If you want to work with the last element then just use
tc.ComponentPresentation cp = cmp[cmp.Count - 1];
//Do anything with cp here
That's it