beginner question: foreach .. else?

[Ted On The Net]

hi, I'm just learning C# after being a Delphi coder for waayyy to long :D I was wondering, why isn't it possible to use an else statement with the foreach statement? Check out my quick and dirty demo code:

namespace ConsoleApplication
{
class Product
{
public string Code { get; set; }
public string Description { get; set; }

}

class Program
{
    static void Main(string\[\] args)
    {
        //create some enumerable list
        IEnumerable<Product> myProductList = new List<Product>
                                     {
                                         new Product() {Code = "CDR", Description = "CD-Rom"},
                                         new Product() {Code = "DVD", Description = "DVD-Rom"},
                                         new Product() {Code = "BRD", Description = "BlueRay Disc"},
                                     };

        //select some products with LINQ
        var myProductSelection = (from aProduct in myProductList where aProduct.Code.StartsWith("R") select aProduct);

        //Print header text
        Console.WriteLine("The products that were found:");

        //loop through products in selection
        foreach (var aProduct in myProductSelection)
        {
            Console.WriteLine("Found product: " + aProduct.Code);
        }
      
        //pause to check results
        Console.ReadKey();            
    }
}

}

The above code returns nothing, since none of the product codes start with a "R". Would be nice if I could do this when my result is empty:

//Print header text
Console.WriteLine("The products that were found:");

//loop through products in selection
foreach (var aProduct in myProductSelection)
{
Console.WriteLine("Found product: " + aProduct.Code);
}
else
{
Console.WriteLine("No products were found!");
}

Just some ranting.. any good solutions to this unlike something like this?

//Print header text
Console.WriteLine("The products that were found:");

int x = 0;
//loop through products in selection
foreach (var aProduct in myProductSelection)
{
x++;
Console.WriteLine("Found product: " + aProduct.Code);
}

if (x > 0)
Console.WriteLine("No products were found!");

thx for any suggestions offered :)

- Life would be so much easier if I had the source code! - If C#

[Lost User]

Ted On The Net wrote:

Just some ranting.. any good solutions to this unlike something like this?

I can only think of 1 fundamentally different solution - explicitly test for the number of items in myProductSelection. Personally I would set a bool to true in the foreach rather than counting the iterations, but that is not that much different from the solution you gave. There is no build-in way to do this, as far as I know.

[kevinnicol]

does myProductSelection have a count or a length? Most strucutres that implement IEnumerable do. If so just check to see if the count is greater than zero.

[Ted On The Net]

yes, it does. One could implement it like this:

if (myProductSelection.Count() != 0)
{
//loop through products in selection
foreach (var aProduct in myProductSelection)
{
Console.WriteLine("Found product:" + aProduct.Code);
}
}
else
{
Console.WriteLine("No products found!");
}

But why should I? If the foreach loop doesn't get executed, I know I've got the same result as if I used the above if-statement. So imo this gives me redundant code. Or do you disagree?

- Life would be so much easier if I had the source code! - If C# had true garbage collection, most applications would delete themselves upon execution ;)

[Paulo Zemek]

I understand why you want this, but there is no implicit way of doing it. But, think that using foreach is a replacement for getting the enumerator, calling while(enumerator.MoveNext()) and setting a variable to enumerator.Current. (and at the end calling Dispose, if possible). So, the best solution for this is doing something like:

using(var enumerator = enumerable.GetEnumerator())
{
if (enumerator.MoveNext())
{
do
{
var someVariable = enumerator.Current;

  ... the loop code...
}
while(enumerator.MoveNext());

}
else
{
... the else you want ...
}
}

And you can even create a method using delegates Action<T> for the value and non-generic Action for the else. Something like:

ForEachOrElse(IEnumerable<T> enumerable, Action<T> actionForEachValue, action elseAction)

And to use it you call something like:

ForEachOrElse
(
enumerable,
(value) =>
{
... the code for each value...
},
() =>
{
... the code for else ...
}
);

modified on Tuesday, March 9, 2010 9:34 AM

[Lost User]

Well no offense, but I'm not really convinced that this is the best solution - it is rather confusing especially to people who never "manually" used an enumerator..

[riced]

Ted On The Net wrote:

But why should I?

Because it expresses the intention of the code? I.e. if there are items loop through them otherwise produce message. :)

Regards David R --------------------------------------------------------------- "Every program eventually becomes rococo, and then rubble." - Alan Perlis

[StarBP]

//Print header text
Console.WriteLine("The products that were found:");

//loop through products in selection
foreach (var aProduct in myProductSelection)
{
Console.WriteLine("Found product: " + aProduct.Code);
}
else
{
Console.WriteLine("No products were found!");
}

Try this:

//Print header text
Console.WriteLine("The products that were found:");

//Initialize tracker variable
int productsFound = 0;

//loop through products in selection
foreach (var aProduct in myProductSelection)
{
Console.WriteLine("Found product: " + aProduct.Code);
productsFound++;
}

if (productsFound == 0)
Console.WriteLine("No products were found!");