Linq to objects Predicate Builder
What is the best way to do a conditional query using linq to objects(not linq to sql).
Currently I am using the Predicate builder found here http://www.albahari.com/nutshell/predicatebuilder.aspx and passing the compiled predicate to the IEnumerable.Where and it seems to work nicely.
Example code of what I want to solve:
eg I have this
string keyword1 = "Test1";
string keyword2 = "Test3";
IEnumerable<TestObject> tests = new List<TestObject>()
{
new TestObject() {Name1 = "Test1", Name2 = "Test1"},
new TestObject() {Name1 = "Test2", Name2 = "Test2"},
开发者_运维问答 new TestObject() {Name1 = "Test3", Name2 = "Test3"},
};
if (!String.IsNullOrEmpty(keyword1) && String.IsNullOrEmpty(keyword2))
tests = tests.Where(e => e.Name1.Contains(keyword1));
else if (!String.IsNullOrEmpty(keyword2) && !String.IsNullOrEmpty(keyword1))
tests = tests.Where(e => e.Name2.Contains(keyword2) || e.Name1.Contains(keyword1));
return tests.ToList();
Just change PredicateBuilder
to use delegates instead of expression trees and use lambdas to build the results:
public static class DelegatePredicateBuilder
{
public static Func<T, bool> True<T>() { return f => true; }
public static Func<T, bool> False<T>() { return f => false; }
public static Func<T, bool> Or<T>(this Func<T, bool> expr1,
Func<T, bool> expr2)
{
return t => expr1(t) || expr2(t);
}
public static Func<T, bool> And<T>(this Func<T, bool> expr1,
Func<T, bool> expr2)
{
return t => expr1(t) && expr2(t);
}
}
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