LINQ Exchange

Let's say you have  list of items, and you need to quickly find out if all the items in the list match (or don't match) a given criteria. Maybe you want to know if a list of ints are all even, or if all items in the list start with the letter P. I write a lot of game code, so I'm frequently checking if a list of units (soldiers, tanks, trees, whatever) are within a certain distance of a target.

Important Note: All<> does not return a list of the items
in the collection. It returns a bool indicating if all the items in the
list match an expression.

Microsoft Explanation

Determines whether all elements of a sequence satisfy a condition.

					public static bool All<TSource>
	

					(
	IEnumerable<TSource> source,
	Func<TSource, bool> predicate
	)
	

In the 2.0 days, we would have to do something like this:

C# 2.0 Example

// build a list and see if all items in it are even
List<int> SampleList = new List<int>() { 1, 1, 2, 3, 5, 8, 13 };
bool IsEven = true;
foreach (int item in SampleList)
{
    // if the item is not even, then set the flag and exit the loop
    if ((item % 2) != 0)
    {
        IsEven = false;
        break;
    }
}
Console.WriteLine(string.Format("Are all numbers even? {0}", IsEven));

// Outputs:
// Are all numbers even? False

 

Now with LINQ, we can write more concise code, like this:

C# 3.0 All<> Example

// build a list and see if all items in it are even
List<int> SampleList = new List<int>() { 1, 1, 2, 3, 5, 8, 13 };
bool AllAreEven = SampleList.All(x => x % 2 == 0);
Console.WriteLine(string.Format("Are all numbers even? {0}", AllAreEven));

// Outputs:
// Are all numbers even? False

 

As you can see, LINQ's All<> returns a bool, true if all items in the list match the expression.

If have questions, comments, or suggestion, please feel to post them in the LINQ Exchange Forum

 

Testing an Expression in a C# List using LINQ ALL, 5.0 out of 5 based on 2 ratings

No related posts.

Related posts brought to you by Yet Another Related Posts Plugin.