« LINQKit » : différence entre les versions
De Banane Atomic
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| (12 versions intermédiaires par le même utilisateur non affichées) | |||
| Ligne 1 : | Ligne 1 : | ||
[[Category: | [[Category:.NET Application]] | ||
= Links = | = Links = | ||
* [https://github.com/scottksmith95/LINQKit LINQKit] on GitHub | * [https://github.com/scottksmith95/LINQKit LINQKit] on GitHub | ||
= AsExpandable = | = [https://github.com/scottksmith95/LINQKit#plugging-expressions-into-entitysets--entitycollections-the-solution AsExpandable] = | ||
<kode lang='csharp'> | <kode lang='csharp'> | ||
Expression<Func<User, bool>> expression = x => x.Name.EndsWith("2"); | Expression<Func<User, bool>> expression = x => x.Name.EndsWith("2"); | ||
| Ligne 11 : | Ligne 11 : | ||
// as x.Users is not a IQueryable, Any cannot take an Expression but a Func | // as x.Users is not a IQueryable, Any cannot take an Expression but a Func | ||
// so we need to use Compile to get Func from Expression | // so we need to use Compile to get Func from Expression | ||
context.Groups.Where(x => x.Users. | context.Groups.Where(x => x.Users.Where(expression.Compile())); // Entity Framework will throw an exception | ||
// solution: use AsExpandable | // solution: use AsExpandable | ||
context.Groups.AsExpandable().Where(x => x.Users.Any(expression.Compile())); | context.Groups.AsExpandable().Where(x => x.Users.Any(expression.Compile())); | ||
// Compile never actually runs; AsExpandable will strip out the call to Compile and substitute it with a correct expression tree | |||
</kode> | |||
= [https://github.com/scottksmith95/LINQKit#combining-expressions Combining Expressions] = | |||
== Boolean operations == | |||
<kode lang='csharp'> | |||
Expression<Func<User, bool>> e1 = x => x.Name.StartsWith("U"); | |||
Expression<Func<User, bool>> e2 = x => x.Name.EndsWith("2"); | |||
Expression<Func<User, bool>> e3 = x => e1.Invoke(x) && e2.Invoke(x); | |||
Console.WriteLine(e3.Expand()); // x => (x.Name.StartsWith("U") AndAlso x.Name.EndsWith("2")) | |||
context.Users.Where(e3.Expand()); | |||
</kode> | |||
== Filter operation == | |||
<kode lang='csharp'> | |||
Expression<Func<IEnumerable<int>, IEnumerable<int>>> e1 = l => l.Select(x => x + 1); | |||
Expression<Func<IEnumerable<int>, IEnumerable<int>>> e10 = l => l.Select(x => x + 10); | |||
Expression<Func<IEnumerable<int>, IEnumerable<int>>> combinedExpresions = x => e10.Invoke(e1.Invoke(x)); | |||
Console.WriteLine(combinedExpresions.Expand()); // x => (x.Select(x => x + 1).Select(x => x + 10)) | |||
var list = new[] { 1, 2, 3 }; | |||
var result = combinedExp.Invoke(list).ToList(); // 12, 13, 14 | |||
</kode> | |||
= [https://github.com/scottksmith95/LINQKit#predicatebuilder PredicateBuilder] = | |||
Allow to dynamically construct a lambda expression tree. | |||
<kode lang='csharp'> | |||
var predicate = PredicateBuilder.New<User>(); | |||
predicate = predicate.And(x => x.Name.StartsWith("U")); | |||
predicate = predicate.And(x => x.Name.EndsWith("2")); | |||
context.Users.Where(predicate); | |||
</kode> | |||
= [https://www.nuget.org/packages/LinqKit.Microsoft.EntityFrameworkCore/ Installation] = | |||
<kode lang='bash'> | |||
dotnet add package LinqKit.Microsoft.EntityFrameworkCore | |||
</kode> | </kode> | ||
Dernière version du 12 mars 2023 à 09:38
Links
- LINQKit on GitHub
AsExpandable
|
Expression<Func<User, bool>> expression = x => x.Name.EndsWith("2");
context.Users.Where(expression); // works fine !
// as x.Users is not a IQueryable, Any cannot take an Expression but a Func
// so we need to use Compile to get Func from Expression
context.Groups.Where(x => x.Users.Where(expression.Compile())); // Entity Framework will throw an exception
// solution: use AsExpandable
context.Groups.AsExpandable().Where(x => x.Users.Any(expression.Compile()));
// Compile never actually runs; AsExpandable will strip out the call to Compile and substitute it with a correct expression tree
|
Combining Expressions
Boolean operations
|
|
Expression<Func<User, bool>> e1 = x => x.Name.StartsWith("U");
Expression<Func<User, bool>> e2 = x => x.Name.EndsWith("2");
Expression<Func<User, bool>> e3 = x => e1.Invoke(x) && e2.Invoke(x);
Console.WriteLine(e3.Expand()); // x => (x.Name.StartsWith("U") AndAlso x.Name.EndsWith("2"))
context.Users.Where(e3.Expand());
|
Filter operation
|
|
Expression<Func<IEnumerable<int>, IEnumerable<int>>> e1 = l => l.Select(x => x + 1);
Expression<Func<IEnumerable<int>, IEnumerable<int>>> e10 = l => l.Select(x => x + 10);
Expression<Func<IEnumerable<int>, IEnumerable<int>>> combinedExpresions = x => e10.Invoke(e1.Invoke(x));
Console.WriteLine(combinedExpresions.Expand()); // x => (x.Select(x => x + 1).Select(x => x + 10))
var list = new[] { 1, 2, 3 };
var result = combinedExp.Invoke(list).ToList(); // 12, 13, 14
|
PredicateBuilder
Allow to dynamically construct a lambda expression tree.
|
|
var predicate = PredicateBuilder.New<User>();
predicate = predicate.And(x => x.Name.StartsWith("U"));
predicate = predicate.And(x => x.Name.EndsWith("2"));
context.Users.Where(predicate);
|
Installation
|
dotnet add package LinqKit.Microsoft.EntityFrameworkCore |
