Determine if LINQ Enumerable contains object based on a condition? [duplicate]

问题

This question already has answers here:

Linq Contains method for a object (4 answers)

Closed 6 years ago.

I have an IEnumerable<Project>

I want to know if this list has any element Project.ID == someID.

Is there a way to do that?

回答1:

Yes, you want to use the Any method (documentation).

IEnumerable<Project> projects = SomeMethodReturningProjects();
if(projects.Any(p => p.ID == someID))
{
    //Do something...
}

回答2:

You can use the Any() extension method.

var hasAny = projectList.Any(proj => proj.ID == someID);

Or, if you want to get that record, you can use FirstOrDefault():

var matchedProject = projectList.FirstOrDefault(proj => proj.ID == someID);

This will return null if it finds nothing that matches, but will pull the whole object if it does find it.

回答3:

Using

projects.Any(p => p.ID == someID)  

returns true (a boolean) if the predicate matched for any element.

回答4:

Yes, use the Any extension method:

list.Any(p => p.ID == someID);

来源：https://stackoverflow.com/questions/14883207/determine-if-linq-enumerable-contains-object-based-on-a-condition