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Can a return statement returning the result of a ternary expression be made to not return for one branch of the ternary?

Is it possible to write this if statement in ternary operator (shorthand of c# if)? If yes what would it be?
if (condition)
{
return true;
}
else
{
int a = 2;
}
Thanx everyone in advance. Thank you very much.
Sorry guys if I confused you. I am trying to use ternary operator in this if else block of the method.
public static bool CompareDictionary(this Dictionary<Position, char>
dictionary1,
Dictionary<Position, char> dictionary2, out List<string> wordList)
{
string str = "";
wordList = new List<string>();
foreach (var dic1KeyVal in dictionary1)
{
Position d1key = dic1KeyVal.Key;
char d1Pos = dic1KeyVal.Value;
bool isFound = false;
foreach (var dic2KeyVal in dictionary2)
{
Position d2key = dic2KeyVal.Key;
char d2Pos = dic2KeyVal.Value;
if (d1Pos.Equals(d2Pos) && d1key == d2key)
{
isFound = true;
str = str + d1Pos.ToString();
}
}
if (isFound == false)
{
return false;
}
else
{
wordList.Add(str);
str = "";
}
}
return true;
}

Short Answer
No.
Long Answer
First of all this code does not even need an else:
if (condition)
{
return true;
}
else
{
int a = 2;
}
and can be written as:
if (condition)
{
return true;
}
int a = 2;
Now for ternary operator: Both conditions in a ternary operator must return the same thing. You cannot return a bool in one condition and then assign to a variable in another condition. If you were checking the answer to a question, for example, it would be like this:
return answer == 2 ? true : false;
Whether the answer is correct or not, we return a bool. Or it could be like this:
return answer == 2 ? 1: -1;
But not like this:
return answer == 2 ? true : "wrong"; // will not compile

No. The ternary operator just returns one out of two potential values depending on a condition.
What you can do with the ternary operator is, e.g. int a = condition ? 0 : 2 which would assign the variable a value of either 0 or 2 depending on the value of condition.
Given a more complete example of what you intend to do someone here could potentially come up with a nicer syntax.

How to use an object from try in catch - c#

I want to use an object in catch block, which get me an exception in try block. I'm parsing some strings to int and need to catch the exception when it's impossible and see, what object was mistaken and in what line. Is that possible or not?
Some code dor example. Thanks.
static void Main(string[] args)
{
var result = Parse(new List<string>() { "3;5;7", "qwe;3;70" });
}
public static List<int[]> Parse(List<string> list)
{
try
{
return list.Select(str => str.Split(';'))
.Select(str => Tuple.Create(int.Parse(str[0]), int.Parse(str[1]), int.Parse(str[2])))
/// something happening
.ToList();
}
catch
{
//here in braces I want to know, which element was wrong
//"qwe" and whole line "qwe;3;70"
throw new FormatException($"Wrong line [{}]");
}
}

Declare the line and value item counters outside the try/catch block and increase them in the LINQ expression body:
public static List<int[]> Parse(List<string> list)
{
int line = 0;
int item = 0;
try
{
return list
.Select(str => {
line++;
item = 0;
return str
.Split(';')
.Select(i => { item++; return int.Parse(i); })
.ToArray();
})
.ToList();
}
catch
{
throw new FormatException($"Wrong line [{line}]; item [{item}]");
}
}
Demo: https://dotnetfiddle.net/uGtw7A

You need a reference to the object causing the exception. However as the instance lives only in the scope of the try-block you can´t access it any more (try and catch don´t share the same scope and thus can´t access the same variables) unless you´d declare the reference to that instance outside the try-bloc
As already mentioned in the comments you should use a normal foreach-loop to have access to the current line:
public static List<int[]> Parse(List<string> list)
{
var result = new List<int[]>();
foreach(var str in list)
{
try
{
var values = str.Split(';');
result.Add(Tuple.Create(
int.Parse(values[0]),
int.Parse(values[1]),
int.Parse(values[2]))
);
}
catch
{
//here in braces I want to know, which element was wrong
throw new FormatException($"Wrong line " + str");
}
}
return result;
}
However you can simply avoid all those exceptions by useing TryParse instead which returns false if parsing failed. So this boils down to something like this:
var values = str.Split(';');
int v0, v1, v2;
if(int.TryParse(values[0], out v0 &&
int.TryParse(values[1], out v1 &&
int.TryParse(values[2], out v2 &&))
result.Add(Tuple.Create(v0, v1, v2));
else
throw new FormatException($"Wrong line " + str");

I recommend manually looping through, splitting the data, checking you have enough elements, and then using TryParse on the numbers. I know this is a departure from using Linq, but it's the better way to do this with error checking:
public static List<int[]> Parse(List<string> list)
{
if (list == null)
{
throw new ArgumentNullException("list");
// you can use nameof(list) instead of "list" in newer versions of C#
}
List<int[]> result = new List<int[]>();
// Loop through the entries
for (int i = 0; i < list.Count; ++i)
{
// Be safe and check we don't have a null value
// I'm just skipping the 'bad' entries for now but
// you can throw an error, etc.
if (list[i] == null)
{
// do something about this? (an exception of your choosing, etc.)
continue;
}
// split the entry
string[] entryData = list[i].Split(';');
// check we have 3 items
if (entryData.Length != 3)
{
// do something about this?
continue;
}
// try to parse each item in turn
int a;
int b;
int c;
if (!int.TryParse(entryData[0], out a))
{
// do something about this?
continue;
}
if (!int.TryParse(entryData[1], out b))
{
// do something about this?
continue;
}
if (!int.TryParse(entryData[2], out c))
{
// do something about this?
continue;
}
// add to the results list
result.Add(new int[] { a, b, c });
}
// return the result
return result;
}

Scope is scope. Anything you define inside your try block and don't explicitly pass on is not going to be available in your catch block.
If you need this information you have to iterate manually over the list and try catch each attempt individually...

There are too many problems with your code, you're assuming that parameter list is not null and contains items that can be splitted in 3 strings, and that every string can be safely parsed to int.
If you not have all the above guaranties just check everything:
public static List<int[]> Parse(List<string> list)
{
if (list == null)
{
throw new ArgumentNullException(nameof(list));
}
var arrayOfStringArray = list
.Select(x => x.Split(';'))
.ToArray();
var resultList = new List<int[]>();
for (var i = 0; i < arrayOfStringArray.Length; i++)
{
var arrayOfString = arrayOfStringArray[i];
if (arrayOfString.Length != 3)
{
throw new InvalidOperationException("meaningfull message there!");
}
var arrayOfInt = new int[3];
for (var j = 0; j < arrayOfInt.Length; j++)
{
arrayOfInt[j] = TryParse(arrayOfString[j], i, j);
}
resultList.Add(arrayOfInt);
}
return resultList;
}
static int TryParse(string value, int line, int position)
{
int result;
if (!int.TryParse(value, out result))
{
throw new FormatException($"Item at position {line},{position} is invalid.");
}
return result;
}

I think that you just got a wrong approach here. Yes, using Tuple + Linq would be the laziest way to get your result but you can't generate custom errors as so.
Here is an example of how you can achieve something alike:
static void Main(string[] args)
{
var result = Parse(new List<string>() { "3;5;7", "qwe;3;70" });
}
public static List<Tuple<int, int, int>> Parse(List<string> list)
{
List<Tuple<int, int, int>> result = new List<Tuple<int, int, int>>();
int line = 0;
int errorCol = 0;
try
{
for (line = 0; line < list.Count; line++)
{
string[] curentLine = list[line].Split(';');
int result0, result1, result2;
errorCol = 1;
if (curentLine.Length > 0 && int.TryParse(curentLine[0], out result0))
errorCol = 2;
else
throw new Exception();
if (curentLine.Length > 1 && int.TryParse(curentLine[1], out result1))
errorCol = 3;
else
throw new Exception();
if (curentLine.Length > 2 && int.TryParse(curentLine[2], out result2))
result.Add(new Tuple<int, int, int>(result0, result1, result2));
else
throw new Exception();
}
return result;
}
catch
{
//here in braces I want to know, which element was wrong
throw new FormatException("Wrong line " + line + " col" + errorCol);
}
}
PS: Line and column start at 0 here.

C# Filter Items In A List According To Multiple Criteria

First, what my situation here is...
My SomeObject has a property string Status which I am interested in for this scenario.
Status property can contain "Open", "Closed", "Finished" values exactly.
I have a method called FilterObjects which returns a List<SomeObject>
Method accepts an argument same as its return type, List<SomeObject>
Method is supposed to filter according to following cases explained below and return the list of objects.
The List<SomeObject> I am sending as argument to my method is guaranteed to be in order (through their ID and type).
The cases are (all related to the string Status property I mentioned):
If any item in the list contains Status = "Finished"; then eliminate all other elements that was in the original list and return only the object that has the "Finished" status.
If any item does NOT contain Status = Finished but contains "CLOSED", I need to check if there is any other item that has the value of "Open" after that "CLOSED" one. You can think of this as a "a task can be closed, but can be reopened. But once it is finished, it cannot be reopened".
If it contains a "CLOSED" and does not have any "OPEN" after that item, I will ignore all the items before CLOSED and only return CLOSED object. If it contains "OPEN" after any closed, I need to return anything AFTER that CLOSED, by excluding itself.
I also tried explain the same thing with my awesome MS Paint skills.
The object itself is not really a problem, but my method is something like this:
private List<SomeObject> FilterObjects(List<SomeObject> objectList)
{
var objects = objectList;
var returnList = new List<SomeObject>();
foreach (var obj in objects)
{
if (obj.Status == "Finished")
{
returnList.Add(obj);
return returnList;
}
}
return new List<SomeObject>();
}
Long story short, what would be the best and most efficient way to apply all this logic in this single method? Honestly, I couldn't go further than the first case I already implemented, which is the FINISHED. Could this whole thing be done with some LINQ magic?
It is guaranteed that I receive an ordered list AND I will never get items more than a couple of hundred so the collection will never be massive.
Many thanks in advance for the help.

You can try something like that:
private List<SomeObject> FilterObjects(List<SomeObject> objectList)
{
SomeObject finished = objectList.FirstOrDefault(o => o.Status.Equals("Finished"));
if (finished != null) { return new List<SomeObject> { finished }; }
List<SomeObject> closed = objectList.SkipWhile(o => !o.Status.Equals("Closed")).ToList();
if (closed.Count == 1) { return closed; }
if (closed.Count > 1) { return closed.Skip(1).ToList(); }
// if you need a new list object than return new List<SomeObject>(objectList);
return objectList;
}

I really wouldn't bother using Linq for this, as you will either create an overly complicated instruction to manage or you will require several loop iterations. I would go for something like this instead:
private List<SomeObject> FilterObjects(List<SomeObject> objectList)
{
int lastClosed = -1;
for (int i = 0; i < objectList.Count; i++)
{
if (objectList[i].Status == "Closed")
lastClosed = i;
else if (objectList[i].Status == "Finished")
return new List<SomeObject>() { objectList[i] };
}
if (lastClosed > -1)
if (lastClosed == objectList.Count - 1)
return new List<SomeObject>() { objectList[lastClosed] };
else
return objectList.Skip(lastClosed + 1).ToList();
else
return objectList;
}
EDIT: slightly changed the last bit of code so that it won't trigger an exception if the objectList is empty

LINQ is not well suited and inefficient for scenarios where you need to apply logic based on previous / next elements of a sequence.
The optimal way to apply your logic is to use a single loop and track the Closed status and the position where the status change occurred. At the end you'll return a single element at that position if the last status is Closed, or a range starting at that position otherwise.
static List<SomeObject> FilterObjects(List<SomeObject> objectList)
{
int pos = 0;
bool closed = false;
for (int i = 0; i < objectList.Count; i++)
{
var item = objectList[i];
if (item.Status == "Finished")
return new List<SomeObject> { item };
if (item.Status == (closed ? "Opened" : "Closed"))
{
pos = i;
closed = !closed;
}
}
return objectList.GetRange(pos, closed ? 1 : objectList.Count - pos);
}

I did it this way:
public static IEnumerable<SomeObject> convert(this IEnumerable<SomeObject> input)
{
var finished = input.FirstOrDefault(x => x.Status == "Finished");
if (finished != null)
{
return new List<SomeObject> {finished};
}
return input.Aggregate(new List<SomeObject>(), (a, b) =>
{
if (!a.Any())
{
a.Add(b);
}
else if (b.Status == "Open")
{
if (a.Last().Status == "Closed")
{
a.Remove(a.Last());
}
a.Add(b);
}
else if (b.Status == "Closed")
{
a = new List<SomeObject> {b};
}
return a;
});
}

You can write a method like this. This is bare minimum you will have to add null check and exception handling.
public List<SomeCls> GetResult(List<SomeCls> lstData)
{
List<SomeCls> lstResult;
if(lstData.Any(x=>x.Status=="Finished"))
{
lstResult = lstData.Where(x=>x.Status=="Finished").ToList();
}
else if(lstData.Any(x=>x.Status=="Closed"))
{
// Here assuming that there is only one Closed in whole list
int index = lstData.FindIndex(0,lstData.Count(),x=>x.Status=="Closed");
lstResult = lstData.GetRange(index,lstData.Count()-index);
if(lstResult.Count()!=1) // check if it contains Open.
{
lstResult = lstResult.Where(x=>x.Status=="Open").ToList();
}
}
else // Only Open
{
lstResult = lstData;
}
return lstResult;
}

something like this :
private List<SomeObject> FilterObjects(List<SomeObject> objectList)
{
if (objectList.Where(x => x.Status == "Finished").Any())
{
return objectList.Where(x => x.Status == "Finished").ToList();
}
else if (objectList.Where(x => x.Status == "Closed").Any())
{
if (objectList.FindIndex(x => x.Status == "Closed") == objectList.Count() - 1)
{
return objectList.Where(x => x.Status == "Closed").ToList();
}
else
{
return objectList.GetRange(objectList.FindIndex(x => x.Status == "Closed") + 1, objectList.Count() - (objectList.FindIndex(x => x.Status == "Closed") + 1));
}
}
return objectList;
}

Generic extension method for retrieving 'default' value?

I'm playing around a bit with determining the default values of objects, based on the example here:
https://stackoverflow.com/a/3195792/1293496
This particular extension method was created for System.Type. What I was trying to accomplish was to make this even more generic, where I could do something like this:
int i = 3;
bool amIaDefaultValue = i.IsDefaultValue();
I would expect this to return true if i == 0 (the default value for an int), and false for all other instances.
Here is my initial attempt:
public static bool IsDefaultValue<T>(this T value)
{
var t = typeof(T); // always comes back as object..?
if (t.IsValueType && Nullable.GetUnderlyingType(t) == null)
{
return value.Equals(Activator.CreateInstance<T>());
}
else
{
var defaultValue = default(T);
if (value == null)
return defaultValue == null;
else
return value.Equals(defaultValue);
}
}
On the plus side, I'm able to attach .IsDefaultValue() to any object. Unfortunately, the type of T always comes back as System.Object. I can get the correct type if I set it up this way:
var t = typeof(value);
But if the value happens to be null, I'll get an error straight away. Is there a good workaround for implementing an extension method like this? Or should I stick to the tried and tested route from the example?
Edit
As pointed out by comments, it seems I oversimplified this a bit and missed the root of the problem. Here's what was actually calling my IsDefaultValue():
foreach (var imprintProperty in deltas.GetType().GetProperties())
{
var value = imprintProperty.GetValue(deltas);
if (!value.IsDefaultValue())
{
// get corresponding prop in programmable area
var programmableProp = progarea.GetType().GetProperty(imprintProperty.Name);
if (programmableProp != null)
programmableProp.SetValue(progarea, value);
}
}
And now it becomes obvious that .GetValue is always returning as System.Object. Uff.
Is it still possible to treat the object as its underlying type in the extension method? Sorry for the confusion with this.

Take a look at this:
static class Program
{
static void Main()
{
int a = 1;
Console.WriteLine("a.IsDefaultValue() : " + a.IsDefaultValue());
a = 0;
Console.WriteLine("a.IsDefaultValue() : " + a.IsDefaultValue());
object obj = new object();
Console.WriteLine("obj.IsDefaultValue() : " + obj.IsDefaultValue());
obj = null;
Console.WriteLine("obj.IsDefaultValue() : " + obj.IsDefaultValue());
int? b = 1;
Console.WriteLine("b.IsDefaultValue() : " + b.IsDefaultValue());
b = null;
Console.WriteLine("b.IsDefaultValue() : " + b.IsDefaultValue());
Console.ReadKey(true);
}
static bool IsDefaultValue<T>(this T value)
{
if (ReferenceEquals(value, null))
{
return true;
}
var t = value.GetType();
if (t.IsValueType)
{
return value.Equals(Activator.CreateInstance(value.GetType()));
}
return false;
}
}
Apparently works (I've to say that I was convinced that the other way should have worked but not)

Using lambda expression to check filepath is valid c#

I am trying to check whether a file path is valid using the following code
foreach (int i in UniqueRandom(0, 4))
{
var wbImage = getCharBitmap(c, rndFolder, i);
}
The UniqueRandom method generates non repeating random numbers between 0 to 4. Each number i represents a file name, which may or may not exist. If the file exist, the getCharBitmap method will return a WritableBitmap object, otherwise, it will return null.
I want to integrate a lambda expression to check whether the method returns null or not, then, if it's not null, I want to remember the i value and exit the foreach loop right away.
How to do this efficiently with the least amount of code?

Try
var firstExisting = UniqueRandom(0, 4)
.Select(i => new
{
Bitmap = GetCharBitmap(c, rndFolder, i),
Number = i
})
.FirstOrDefault(x => x.Bitmap != null);
if (firstExisting != null)
{
int j = firstExisting.Number;
}
Or the same without LINQ:
private static int FirstExisting()
{
foreach (int i in UniqueRandom(0, 4))
{
var wbImage = GetCharBitmap(c, rndFolder, i);
if (wbImage != null)
{
return i;
}
}
throw new Exception("No existing found"); // or return say -1
}