یک نکتهی تکمیلی
تا دات نت 7 میتوان از روش زیر برای انتخاب تصادفی اعضای یک مجموعه استفاده کرد:
MyCollection.OrderBy(x => Random.Shared.Next()).Take(10)
MyCollection.OrderBy(x => Random.Shared.Next()).Take(10)
public static int Add(in int number1, in int number2) { number1 = 5; // Cannot assign to variable 'in int' because it is a readonly variable return number1 + number2; }
<ItemGroup> <PackageReference Include="BenchmarkDotNet" Version="0.10.12" /> </ItemGroup>
using BenchmarkDotNet.Attributes; namespace CS72Tests { public struct Input { public decimal Number1; public decimal Number2; } [MemoryDiagnoser] public class InBenchmarking { const int loops = 50000000; Input inputInstance = new Input(); [Benchmark(Baseline = true)] public decimal RunNormalLoop_Pass_By_Value() { decimal result = 0M; for (int i = 0; i < loops; i++) { result = Run(inputInstance); } return result; } [Benchmark] public decimal RunInLoop_Pass_By_Reference() { decimal result = 0M; for (int i = 0; i < loops; i++) { result = RunIn(in inputInstance); } return result; } public decimal Run(Input input) { return input.Number1; } public decimal RunIn(in Input input) { return input.Number1; } } }
static void Main(string[] args) { var summary = BenchmarkRunner.Run<InBenchmarking>();
Method | Mean | Error | StdDev | Scaled | Allocated | ---------------------------- |----------:|---------:|---------:|-------:|----------:| RunNormalLoop_Pass_By_Value | 280.04 ms | 2.219 ms | 1.733 ms | 1.00 | 0 B | RunInLoop_Pass_By_Reference | 91.75 ms | 1.733 ms | 1.780 ms | 0.33 | 0 B |
public static class Factorial { public static int Calculate(in this int num) { int result = 1; for (int i = num; i > 1; i--) result *= i; return result; } }
int num = 3; Console.WriteLine($"(in num) -> {Factorial.Calculate(in num)}"); Console.WriteLine($"(num) -> {Factorial.Calculate(num)}"); Console.WriteLine($"num. -> {num.Calculate()}");
(in num) -> 6 (num) -> 6 num. -> 6
public class CX { public void A(Input a) { Console.WriteLine("int a"); } public void A(in Input a) { Console.WriteLine("in int a"); } }
public class Y { public void Test() { var inputInstance = new Input(); var cx = new CX(); cx.A(inputInstance); // The call is ambiguous between the following methods or properties: 'CX.A(Input)' and 'CX.A(in Input)' } }
public IEnumerable<int> B(in int a) // Iterators cannot have ref or out parameters { Console.WriteLine("in int a"); yield return 1; }
public async Task C(in int a) // Async methods cannot have ref or out parameters { await Task.Delay(1000); }
using System; namespace CS72Tests { struct MyStruct { public int MyValue { get; set; } public void UpdateMyValue(int value) { MyValue = value; } } public static class TestInStructs { public static void Run() { var myStruct = new MyStruct(); myStruct.UpdateMyValue(1); UpdateMyValue(myStruct); Console.WriteLine(myStruct.MyValue); } static void UpdateMyValue(in MyStruct myStruct) { myStruct.UpdateMyValue(5); } } }
static void UpdateMyValue(in MyStruct myStruct) { myStruct.MyValue = 5; // Cannot assign to a member of variable 'in MyStruct' because it is a readonly variable myStruct.UpdateMyValue(5); }
using System;
using System.IO;
namespace NHibernate.Helper.DbSpecific
{
public class SqlCEDbHelper
{
const string engineTypeName = "System.Data.SqlServerCe.SqlCeEngine, System.Data.SqlServerCe";
/// <summary>
/// note: this method will delete existing db and then creates a new one.
/// </summary>
/// <param name="filename"></param>
/// <param name="password"></param>
public static void CreateEmptyDatabaseFile(string filename, string password = "")
{
if (File.Exists(filename))
File.Delete(filename);
var type = System.Type.GetType(engineTypeName);
var localConnectionString = type.GetProperty("LocalConnectionString");
var createDatabase = type.GetMethod("CreateDatabase");
var engine = Activator.CreateInstance(type);
string connectionStr = string.Format("Data Source='{0}';Password={1};Encrypt Database=True", filename, password);
if (string.IsNullOrWhiteSpace(password))
connectionStr = string.Format("Data Source='{0}'", filename);
localConnectionString.SetValue(
obj: engine,
value: connectionStr,
index: null);
createDatabase.Invoke(engine, new object[0]);
}
/// <summary>
/// use this method to compact or encrypt existing db or decrypt it to a new db with all records
/// </summary>
/// <param name="sourceConnection"></param>
/// <param name="destConnection"></param>
public static void CompactDatabase(string sourceConnection, string destConnection)
{
var type = System.Type.GetType(engineTypeName);
var engine = Activator.CreateInstance(type);
var localConnectionString = type.GetProperty("LocalConnectionString");
localConnectionString.SetValue(
obj: engine,
value: sourceConnection,
index: null);
var compactDatabase = type.GetMethod("Compact");
compactDatabase.Invoke(engine, new object[] { destConnection });
}
}
}
Data Source=c:\path\db.sdf;Password=1234;Encrypt Database=True
private Configuration getConfig()
{
var configure = new Configuration();
configure.SessionFactoryName("BuildIt");
configure.DataBaseIntegration(db =>
{
db.ConnectionProvider<DriverConnectionProvider>();
db.Dialect<MsSqlCe40Dialect>();
db.Driver<SqlServerCeDriver>();
db.KeywordsAutoImport = Hbm2DDLKeyWords.AutoQuote;
db.IsolationLevel = IsolationLevel.ReadCommitted;
db.ConnectionString = ConnectionString;
db.Timeout = 10;
//for testing ...
db.LogFormattedSql = true;
db.LogSqlInConsole = true;
});
return configure;
}
PM> Install-Package DNTProfiler.EntityFramework.Core
<configuration> <entityFramework> <interceptors> <interceptor type="DNTProfiler.EntityFramework.Core.DatabaseLogger, DNTProfiler.EntityFramework.Core"> <parameters> <parameter value="http://localhost:8080" /> <parameter value="|DataDirectory|\ErrorsLog.Log" /> </parameters> </interceptor> </interceptors> </entityFramework> </configuration>
CATNETCmd /file:"I:\prog\bin\prog.dll" /search:"I:\prog" /report:"I:\prog\report.xsl" /rule:"J:\microsoft\cat.net\Rules"