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improve linq query support
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14 files changed

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‎CSharpFunctionalExtensions.Examples/LinqQuery/ResultQueryExamples.cs‎

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using System;
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using System.Text.RegularExpressions;
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using System.Threading.Tasks;
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namespace CSharpFunctionalExtensions.Examples.LinqQuery
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{
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/// <summary>
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/// Demonstrates using LINQ query syntax (sugar) as an alternative to
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/// fluent method chaining to compose operations in a monadic style,
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/// analogous to F# computation expressions or Haskell's do-notation.
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/// </summary>
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public class ResultQueryExamples
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{
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public async Task Demo()
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{
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// Using the LINQ query syntax:
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var validCustomer =
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from email in Email.Create("[email protected]")
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from name in CustomerName.Create("jsmith")
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select new Customer(name, email);
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// Equivalent to:
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var validCustomer_ = Email
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.Create("[email protected]")
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.Bind(email =>
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CustomerName.Create("jsmith").Map(name => new Customer(name, email))
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);
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// Success(Customer(Name: jsmith, Email: [email protected]))
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Console.WriteLine(validCustomer);
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var invalidCustomer =
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from email in Email.Create("no email")
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from name in CustomerName.Create("jsmith")
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select new Customer(name, email);
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// Failure(E-mail is invalid)
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Console.WriteLine(invalidCustomer);
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//------------------------------------------------------------------------------
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// Also works with async methods.
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var billing = await (
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from customer in CustomerRepository.GetByIdAsync(1) // Task<Result<Customer>>
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from billingInfo in PaymentGateway.ChargeCustomerAsync(customer, 1_000) // Task<Result<BillingInfo>>
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select billingInfo
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);
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// Equivalent to:
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var billing_ = await CustomerRepository
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.GetByIdAsync(1)
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.Bind(customer => PaymentGateway.ChargeCustomerAsync(customer, 1_000));
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// Success(BillingInfo(Customer: [email protected], ChargeAmount: 1000))
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Console.WriteLine(billing);
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var failedBilling = await (
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from customer in CustomerRepository.GetByIdAsync(1)
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from billingInfo in PaymentGateway.ChargeCustomerAsync(customer, 5_000_000)
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select billingInfo
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);
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// Failure(Insufficient balance.)
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Console.WriteLine(failedBilling);
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}
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}
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public class Email
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{
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private readonly string _value;
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private Email(string value)
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{
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_value = value;
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}
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public override string ToString()
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{
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return _value;
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}
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public static Result<Email> Create(string email)
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{
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if (string.IsNullOrWhiteSpace(email))
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return Result.Failure<Email>("E-mail can't be empty");
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if (email.Length > 100)
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return Result.Failure<Email>("E-mail is too long");
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if (!Regex.IsMatch(email, @"^([\w\.\-]+)@([\w\-]+)((\.(\w){2,3})+)$"))
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return Result.Failure<Email>("E-mail is invalid");
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return Result.Success(new Email(email));
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}
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}
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public class CustomerName
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{
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private readonly string _value;
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private CustomerName(string value)
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{
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_value = value;
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}
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public override string ToString()
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{
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return _value;
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}
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public static Result<CustomerName> Create(string name)
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{
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if (string.IsNullOrWhiteSpace(name))
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return Result.Failure<CustomerName>("Name can't be empty");
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if (name.Length > 50)
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return Result.Failure<CustomerName>("Name is too long");
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return Result.Success(new CustomerName(name));
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}
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}
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public class Customer
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{
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public CustomerName Name { get; private set; }
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public Email Email { get; private set; }
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public Customer(CustomerName name, Email email)
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{
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if (name == null)
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throw new ArgumentNullException("name");
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if (email == null)
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throw new ArgumentNullException("email");
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Name = name;
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Email = email;
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}
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public override string ToString()
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{
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return $"{nameof(Customer)}({nameof(Name)}: {Name}, {nameof(Email)}: {Email})";
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}
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}
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public class CustomerRepository
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{
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public static async Task<Result<Customer>> GetByIdAsync(int id)
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{
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var customer =
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from email in Email.Create("[email protected]")
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from name in CustomerName.Create("jsmith")
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select new Customer(name, email);
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return customer;
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}
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}
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public class BillingInfo
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{
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public Customer Customer { get; set; }
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public decimal ChargeAmount { get; set; }
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public override string ToString()
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{
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return $"{nameof(BillingInfo)}({nameof(Customer)}: {Customer.Email}, {nameof(ChargeAmount)}: {ChargeAmount})";
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}
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}
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public class PaymentGateway
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{
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public static async Task<Result<BillingInfo>> ChargeCustomerAsync(
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Customer customer,
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decimal chargeAmount
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)
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{
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if (chargeAmount > 1_000_000)
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return Result.Failure<BillingInfo>("Insufficient balance");
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return Result.Success(
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new BillingInfo { Customer = customer, ChargeAmount = chargeAmount }
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);
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}
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}
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}

‎CSharpFunctionalExtensions/Maybe/Extensions/Select.Task.cs‎

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using System;
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using System.Threading.Tasks;
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namespace CSharpFunctionalExtensions
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{
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public static partial class MaybeExtensions
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{
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/// <summary>
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/// This method should be used in linq queries. We recommend using Map method.
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/// </summary>
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public static Task<Maybe<K>> Select<T, K>(this Task<Maybe<T>> maybe, Func<T, K> selector)
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{
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return maybe.Map(selector);
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}
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}
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}

‎CSharpFunctionalExtensions/Maybe/Extensions/Select.ValueTask.cs‎

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#if NET5_0_OR_GREATER
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using System;
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using System.Threading.Tasks;
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namespace CSharpFunctionalExtensions.ValueTasks
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{
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public static partial class MaybeExtensions
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{
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/// <summary>
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/// This method should be used in linq queries. We recommend using Map method.
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/// </summary>
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public static ValueTask<Maybe<K>> Select<T, K>(in this ValueTask<Maybe<T>> maybe, Func<T, K> selector)
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{
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return maybe.Map(selector);
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}
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}
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}
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#endif

‎CSharpFunctionalExtensions/Maybe/Extensions/SelectMany.Task.Left.cs‎

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using System;
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using System.Threading.Tasks;
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namespace CSharpFunctionalExtensions
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{
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public static partial class MaybeExtensions
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{
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/// <summary>
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/// This method should be used in linq queries. We recommend using Bind method.
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/// </summary>
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public static async Task<Maybe<V>> SelectMany<T, U, V>(
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this Task<Maybe<T>> maybeTask,
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Func<T, Maybe<U>> selector,
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Func<T, U, V> project)
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{
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Maybe<T> maybe = await maybeTask.DefaultAwait();
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return maybe.SelectMany(selector, project);
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}
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}
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}

‎CSharpFunctionalExtensions/Maybe/Extensions/SelectMany.Task.Right.cs‎

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using System;
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using System.Threading.Tasks;
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namespace CSharpFunctionalExtensions
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{
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public static partial class MaybeExtensions
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{
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/// <summary>
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/// This method should be used in linq queries. We recommend using Bind method.
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/// </summary>
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public static Task<Maybe<V>> SelectMany<T, U, V>(
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this Maybe<T> maybe,
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Func<T, Task<Maybe<U>>> selector,
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Func<T, U, V> project)
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{
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return maybe
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.Bind(selector)
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.Map(x => project(maybe.Value, x));
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}
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}
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}

‎CSharpFunctionalExtensions/Maybe/Extensions/SelectMany.Task.cs‎

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using System;
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using System.Threading.Tasks;
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namespace CSharpFunctionalExtensions
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{
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public static partial class MaybeExtensions
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{
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/// <summary>
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/// This method should be used in linq queries. We recommend using Bind method.
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/// </summary>
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public static Task<Maybe<K>> SelectMany<T, K>(
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this Maybe<T> maybe,
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Func<T, Task<Maybe<K>>> selector)
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{
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return maybe.Bind(selector);
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}
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/// <summary>
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/// This method should be used in linq queries. We recommend using Bind method.
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/// </summary>
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public static Task<Maybe<K>> SelectMany<T, K>(
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this Task<Maybe<T>> maybeTask,
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Func<T, Task<Maybe<K>>> selector)
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{
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return maybeTask.Bind(selector);
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}
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/// <summary>
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/// This method should be used in linq queries. We recommend using Bind method.
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/// </summary>
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public static async Task<Maybe<V>> SelectMany<T, U, V>(
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this Task<Maybe<T>> maybeTask,
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Func<T, Task<Maybe<U>>> selector,
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Func<T, U, V> project)
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{
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var maybe = await maybeTask.DefaultAwait();
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return await maybe.SelectMany(selector, project).DefaultAwait();
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}
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}
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}

‎CSharpFunctionalExtensions/Maybe/Extensions/SelectMany.ValueTask.Left.cs‎

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#if NET5_0_OR_GREATER
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using System;
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using System.Threading.Tasks;
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namespace CSharpFunctionalExtensions.ValueTasks
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{
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public static partial class MaybeExtensions
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{
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/// <summary>
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/// This method should be used in linq queries. We recommend using Bind method.
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/// </summary>
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public static async ValueTask<Maybe<V>> SelectMany<T, U, V>(
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this ValueTask<Maybe<T>> maybeTask,
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Func<T, Maybe<U>> selector,
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Func<T, U, V> project)
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{
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Maybe<T> maybe = await maybeTask;
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return maybe.SelectMany(selector, project);
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}
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}
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}
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#endif

‎CSharpFunctionalExtensions/Maybe/Extensions/SelectMany.ValueTask.Right.cs‎

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#if NET5_0_OR_GREATER
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using System;
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using System.Threading.Tasks;
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namespace CSharpFunctionalExtensions.ValueTasks
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{
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public static partial class MaybeExtensions
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{
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/// <summary>
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/// This method should be used in linq queries. We recommend using Bind method.
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/// </summary>
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public static ValueTask<Maybe<V>> SelectMany<T, U, V>(
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this Maybe<T> maybe,
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Func<T, ValueTask<Maybe<U>>> selector,
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Func<T, U, V> project)
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{
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return maybe
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.Bind(selector)
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.Map(x => project(maybe.Value, x));
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}
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}
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}
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#endif

‎CSharpFunctionalExtensions/Maybe/Extensions/SelectMany.ValueTask.cs‎

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#if NET5_0_OR_GREATER
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using System;
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using System.Threading.Tasks;
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namespace CSharpFunctionalExtensions.ValueTasks
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{
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public static partial class MaybeExtensions
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{
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/// <summary>
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/// This method should be used in linq queries. We recommend using Bind method.
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/// </summary>
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public static ValueTask<Maybe<K>> SelectMany<T, K>(
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this Maybe<T> maybe,
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Func<T, ValueTask<Maybe<K>>> selector)
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{
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return maybe.Bind(selector);
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}
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/// <summary>
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/// This method should be used in linq queries. We recommend using Bind method.
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/// </summary>
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public static ValueTask<Maybe<K>> SelectMany<T, K>(
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this ValueTask<Maybe<T>> maybeTask,
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Func<T, ValueTask<Maybe<K>>> selector)
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{
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return maybeTask.Bind(selector);
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}
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/// <summary>
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/// This method should be used in linq queries. We recommend using Bind method.
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/// </summary>
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public static async ValueTask<Maybe<V>> SelectMany<T, U, V>(
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this ValueTask<Maybe<T>> maybeTask,
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Func<T, ValueTask<Maybe<U>>> selector,
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Func<T, U, V> project)
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{
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var maybe = await maybeTask;
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return await maybe.SelectMany(selector, project);
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}
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}
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}
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#endif

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