CODEWITHSUNDEEP
c#.netpredicate
Abe Miessler
Abe Miessler

Reputation: 85116

How would I define this predicate as a function?

Not sure if I have the title right on this one, feel free to correct me.

I have code similar to the following:

string myValue = "aaa";
List<ListItem> myList = CreateMyList();
myList.Find(t=>t.Value == myValue );

I would like to create a Predicate function that does the same thing. I am able to implement it if I do not need to pass in myValue:

   ...
   List<ListItem> myList = CreateMyList();
   myList.Find(SelectByValue);
   ...
}

static bool SelectByValue(ListItem li)
{                      //***myValue is now hardcoded***
    return li.Value == "aaa";
}

But I would like to be able to specify what "aaa" should be when I make the call to the predicate function. How can this be done?

Upvotes: 1

Views: 191

Answers (2)

Jon Skeet
Jon Skeet

Reputation: 1502816

Rather than returning a bool, make it return a Predicate<ListItem>:

static Predicate<ListItem> SelectByValue(String target)
{
    return delegate(ListItem li) { return li.Value == target; };
}

Then call the method:

myList.Find(SelectByValue("foo"));

Note that C# 3 introduces lambda expressions making this slightly simpler:

static Predicate<ListItem> SelectByValue(String target)
{
    return li => li.Value == target;
}

... and in .NET 3.5 and higher, it's generally more idiomatic to use LINQ than the List<T>-specific methods.

Upvotes: 5

Muhammad Hasan Khan
Muhammad Hasan Khan

Reputation: 35146

static Predicate<ListItem> SelectByValue(string value)
{
    return item=>li.Value == value;
}

Upvotes: 3

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