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What is an "index out of range" exception, and how do I fix it? [duplicate]
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Closed 8 years ago.
I seem to be having a problem with C# 2008. I am creating a simple program that shows a list of all the files within a specific folder. I chose to experiment with system files in the Windows folder. It shows a list of the files and then an exception occurs. Here is the code:
if (EnterNumber == "1")
{
Console.WriteLine("Files");
DirectoryInfo folderInfo = new DirectoryInfo("F:\\WINDOWS");
FileInfo[] Files = folderInfo.GetFiles();
String UserChoice = Console.ReadLine();
for (int index = 0; index < Files.Length; index++)
{
Console.WriteLine("{0}, {1} ({2})", index++, Files[index].Name, Files[index].Length);
}
Console.Write("Return To Main Menu?: ");
if (UserChoice == "y")
{
So the user presses the number 1 to show the files and they appear in a list. It displays the files in the Windows folder. But can you see the console write line with several pieces of information? A line appears with a message to an error. The exception occurs saying that the index is outside the bounds of the array. I know what an array is, but I have a problem applying that information. If you can tell me of a way to remove this error then I would be grateful. So the files show normally, no matter how long the list is. Also, is there a way to allow the user to clear the screen and return to the main menu? I have tried the clear function, but should I keep adding the if statements that allow the user to input their choice again?
for (int index = 0; index < Files.Length; index++)
{
Console.WriteLine("{0}, {1} ({2})", index++, Files[index].Name, Files [index].Length);
}
The problem is in your writeline, you are incrementing index again. I would just change it to index and not index++.
Try changing:
Console.WriteLine("{0}, {1} ({2})", index++, Files[index].Name, Files[index].Length);
to:
Console.WriteLine("{0}, {1} ({2})", index, Files[index].Name, Files[index].Length);
The ++ operator (MSDN documentation) is being incremented twice in your loop, when you probably only want to go one at a time.
Related
I would like to write a snippet in VS Code that writes a "switch" expression (in Javascript), but one where I can define the number of cases.
Currently there is a snippet that produces the outline of a switch expression with 1 case, and allows you to tab into the condition, case name, and the code contained within.
I want to be able to type "switch5" ("5" being any number) and a switch with 5 cases to be created, where I can tab through the relevant code within.
I know the snippets are written in a JSON file, can I include such conditional logic in this, or is it not possible?
Thanks!
The short answer is that you cannot do that kind of thing in a standard vscode snippet because it cannot dynamically evaluate any input outside of its designated variables with some limited workarounds like I'll mention next.
You might - I and others have written answers on SO about his - type your various case values first and then trigger a snippet tat would transform them into a switch statement. It is sort of doing it backwords but it might be possible.
There are extensions, however, that do allow you to evaluate javascript right in a snippet or setting and output the result. macro-commander is one such extension. I'll show another simpler extension doing what you want: HyperSnips.
In your javascript.hsnips:
snippet `switch(\d)` "add number of cases to a switch statement" A
``
let numCases = Number(m[1]) // 'm' is an array of regex capture groups
let caseString = ''
if (numCases) { // if not 'switch0'
let tabStopNum = 1
caseString = `switch (\${${tabStopNum++}:key}) {\n`
for (let index = 0; index < m[1]; index++) {
caseString += `\tcase \${${tabStopNum++}:value}:\n\t\t\$${tabStopNum++}\n`
caseString += '\t\tbreak;\n\n'
}
caseString += '\tdefault:\n'
caseString += '\t\tbreak;\n}\n'
}
rv = `${caseString}` // return value
``
endsnippet
The trickiest part was getting the unknown number of tabstops to work correctly. This is how I did it:
\${${tabStopNum++}:key}
which will resolve to ${n:defaultValue} where n gets incremented every time a tabstop is inserted. And :defaultValue is an optional default value to that tabstop. If you don't need a defaultValue just use \$${tabStopNum++} there.
See https://stackoverflow.com/a/62562886/836330 for more info on how to set up HyperSnips.
Attempting to loop through this array, stored in a JSON file. I want to be able to check if a quote is saved and then display it depending on whether it is saved or not.
_toggleCheck() {
var checked = !this.state.checked;
this.setState({ checked: checked });
// For loop to run through arrray and update booleans
for(int i = 0; i<quotesArray.length-1; i++;){
quotes.quotesArray[i].isSaved = checked;
}
this.props.onChange && this.props.onChange(this.props.name, checked);
}
In attempting to do this, I have come across this error and can not resolve it. Line 63 is the beginning of the for loop. I dont know how to use a for loop in react native and cant find any tutorials on line.
for(int i = 0; i<quotesArray.length-1; i++;){
^ remove this semicolon
By the way, are you sure you want i < quotesArray.length - 1 instead of i < quotesArray.length? You're skipping the last element when you add -1.
When using .setChoices() It looks for an array of created choices. If it is a multiple choice question it can be formatted either createChoice(value) or createChoice(value, navigationType).
When looking at a choice you put in something like: var cPage = chkItem.getChoices()[j].getGotoPage();
This will produce either the page object or a Null value.
The problem is when a question is set to "go to page based on answer" and they have not set a page for every entry, and left the default to continue it also reads it (in my case cPage), as null. This means if I want to go through each choice to capture it, modify it, then push it back out to the question, it my ending Array that I push out consists of both Null and Objects, which produces an error.
My workaround for questions without pages is for the script to forcibly change the question to handle page navigation but set everyone to CONTINUE.
I would like to find a way to check if the question has "go to page based on answer" checked and if not then be able to create choices using just the value.
Figured it out: I need to check the first choice if it has a PageNavigationType(). If it does then the box is checked. If null then it is not checked. I have not written the code to fully test this but the theory should work. (I was checking against just the goToPage type which is why it didn't work before. )
var choicecount = chkItem.getChoices().length-1;
var hasNavType = chkItem.getChoices()[0].getPageNavigationType(); //if null
for (var j = 0; j <= choicecount; ++j) {
var cValue = chkItem.getChoices()[j].getValue();
var cPage = chkItem.getChoices()[j].getGotoPage();
var cNav = chkItem.getChoices()[j].getPageNavigationType();
// Logger.log(j+" "+cPage);
if (cValue != reValues[0]){
if (hasNavType == null){
newChoices.push(chkItem.createChoice(cValue));
} else {
if (cPage == null){
newChoices.push(chkItem.createChoice(cValue,cNav));
} else {
newChoices.push(chkItem.createChoice(cValue,cPage));
}
}
}
}
I cant seem to work out to trace the content of a data grid i have populated with info;
Once I can work out how to trace it or each row i would push it into a new array for exporting.
so for example: i have a datagrid instanceNamed(info) //populated from a CVS file; text file//
containing 150 rows and 15 columns. I would simply like to trace this in the output window .From then i will work out how to write to disk.
i have been searching around but cant seem to find a solution to this problem.
thank you
Check out this tutorial: Using the Flex Automation API with Fluint
What you need is implemented in the getValuesFromGrid()-method. Check how the DataGridTabularData is used.
I have worked out how to trace a single cell or an entire DataGrid, Below is an example:
function trace_dataGrid(){
for (var k:Number = 0; k < DataGrid.length - 1; k++) {
var info += DataGrid.getItemAt(k).Team_name + "," +
DataGrid.getItemAt(k).Player_name+"\r\n";
trace(info);
}
}
OutPut
Australia Footy,Bob
Sydney Soccer,David
Australia Cricket,Jim
RunThrough:
First creat a loop counter "k" which is checking the Data Grid "length"
"get item AT" will check the first location,matching to the variable in the DataGrid
"TeamName" / " PlayerName is the next reference. After this has done it will repeat this "k++" Same structure until the condition is met(counter == datagrids Length-1) for better understanding the best bet would be how to structure Arrays,tuts ect.
I have something like 40 million TIFF documents, all 1-bit single page duplex. In about 40% of cases, the back image of these TIFFs is 'blank' and I'd like to remove them before I do a load to a CMS to reduce space requirements.
Is there a simple method to look at the data content of each page and delete it if it falls under a preset threshold, say 2% 'black'?
I'm technology agnostic on this one, but a C# solution would probably be the easiest to support. Problem is, I've no image manipulation experience so don't really know where to start.
Edit to add: The images are old scans and so are 'dirty', so this is not expected to be an exact science. The threshold would need to be set to avoid the chance of false positives.
You probably should:
open each image
iterate through its pages (using Bitmap.GetFrameCount / Bitmap.SelectActiveFrame methods)
access bits of each page (using Bitmap.LockBits method)
analyze contents of each page (simple loop)
if contents is worthwhile then copy data to another image (Bitmap.LockBits and a loop)
This task isn't particularly complex but will require some code to be written. This site contains some samples that you may search for using method names as keywords).
P.S. I assume that all of images can be successfully loaded into a System.Drawing.Bitmap.
You can do something like that with DotImage (disclaimer, I work for Atalasoft and have written most of the underlying classes that you'd be using). The code to do it will look something like this:
public void RemoveBlankPages(Stream source stm)
{
List<int> blanks = new List<int>();
if (GetBlankPages(stm, blanks)) {
// all pages blank - delete file? Skip? Your choice.
}
else {
// memory stream is convenient - maybe a temp file instead?
using (MemoryStream ostm = new MemoryStream()) {
// pulls out all the blanks and writes to the temp stream
stm.Seek(0, SeekOrigin.Begin);
RemoveBlanks(blanks, stm, ostm);
CopyStream(ostm, stm); // copies first stm to second, truncating at end
}
}
}
private bool GetBlankPages(Stream stm, List<int> blanks)
{
TiffDecoder decoder = new TiffDecoder();
ImageInfo info = decoder.GetImageInfo(stm);
for (int i=0; i < info.FrameCount; i++) {
try {
stm.Seek(0, SeekOrigin.Begin);
using (AtalaImage image = decoder.Read(stm, i, null)) {
if (IsBlankPage(image)) blanks.Add(i);
}
}
catch {
// bad file - skip? could also try to remove the bad page:
blanks.Add(i);
}
}
return blanks.Count == info.FrameCount;
}
private bool IsBlankPage(AtalaImage image)
{
// you might want to configure the command to do noise removal and black border
// removal (or not) first.
BlankPageDetectionCommand command = new BlankPageDetectionCommand();
BlankPageDetectionResults results = command.Apply(image) as BlankPageDetectionResults;
return results.IsImageBlank;
}
private void RemoveBlanks(List<int> blanks, Stream source, Stream dest)
{
// blanks needs to be sorted low to high, which it will be if generated from
// above
TiffDocument doc = new TiffDocument(source);
int totalRemoved = 0;
foreach (int page in blanks) {
doc.Pages.RemoveAt(page - totalRemoved);
totalRemoved++;
}
doc.Save(dest);
}
You should note that blank page detection is not as simple as "are all the pixels white(-ish)?" since scanning introduces all kinds of interesting artifacts. To get the BlankPageDetectionCommand, you would need the Document Imaging package.
Are you interested in shrinking the files or just want to avoid people wasting their time viewing blank pages? You can do a quick and dirty edit of the files to rid yourself of known blank pages by just patching the second IFD to be 0x00000000. Here's what I mean - TIFF files have a simple layout if you're just navigating through the pages:
TIFF Header (4 bytes)
First IFD offset (4 bytes - typically points to 0x00000008)
IFD:
Number of tags (2-bytes)
{individual TIFF tags} (12-bytes each)
Next IFD offset (4 bytes)
Just patch the "next IFD offset" to a value of 0x00000000 to "unlink" pages beyond the current one.