- اینکه شما بروز یک مشکل رو با یک عدد منفی از یک متد بازگشت می‌دید یعنی هنوز دید زبان C رو دارید. در دات نت وجود استثناءها دقیقا برای ننوشتن return 0 یا -1 و شبیه به آن هست. در این حالت برنامه خودکار در هر سطحی که باشد، ادامه‌اش متوقف میشه و نیازی نیست تا مدام خروجی یک متد رو چک کرد.
- اینکه در یک متد کانکشنی برقرار شده و بسته شده یعنی ضعف کپسوله سازی مفاهیم ADO.NET. نباید این مسایل رو مدام در تمام متدها تکرار کرد. میشه یک متد عمومی ExecSQL درست کرد بجای تکرار مدام یک سری کد.
- یک سری از اشیاء اینترفیس IDisposable رو پیاده سازی میکنند مثل همین شیء اتصالی که ذکر شد. در این حالت میشه از using استفاده کرد بجای try/finally و اون وقت به دوتا using نیاز خواهید داشت یعنی شیء Command هم نیاز به try/finally داره.
public class Student
{
[JsonPropertyName("id")]
public int Id { get; set; }
[JsonPropertyName("name")]
public string Name { get; set; }
}
public class WeatherForecast
{
[Required]
public int TemperatureC { get; set; }
[MinLength(50)]
public string Summary { get; set; }
} [AttributeUsage(AttributeTargets.Class)]
public class CustomDoNothingAttribute: Attribute
{
// Note the type parameter in the constructor
public CustomDoNothingAttribute(Type t)
{
ParamType = t;
}
public Type ParamType { get; }
} [CustomDoNothing(typeof(string))]
public class Student
{
public int Id { get; set; }
public string Name { get; set; }
} [AttributeUsage(AttributeTargets.Class)]
public class CustomDoNothingAttribute<T> : Attribute
where T : class
{
public T ParamType { get; }
}
[CustomDoNothing<string>]
public class Student
{
public int Id { get; set; }
public string Name { get; set; }
} [AttributeUsage(AttributeTargets.Class, AllowMultiple = true)]
public class DecorateAttribute<T> : Attribute where T : class
{
// ....
} [Decorate<LoggerDecorator>]
[Decorate<TimerDecorator>]
public class SimpleWorker
{
// ....
} public class GenericAttribute<T> : Attribute { }
public class GenericType<T>
{
[GenericAttribute<T>] // Not allowed! generic attributes must be fully constructed types.
public string Method1() => default;
[GenericAttribute<string>]
public string Method2() => default;
} Learn how to integrate the CefSharp open-source web browser into a C# WinForms app
Behind the Browser, Part 1: The Basics
The C# Language Integrated Queries ported for Javascript for amazing performance
We’re excited to announce the release of .NET Core 3.0. It includes many improvements, including adding Windows Forms and WPF, adding new JSON APIs, support for ARM64 and improving performance across the board. C# 8 is also part of this release, which includes nullable, async streams, and more patterns. F# 4.7 is included, and focused on relaxing syntax and targeting .NET Standard 2.0. You can start updating existing projects to target .NET Core 3.0 today. The release is compatible with previous versions, making updating easy.
// Behavior 1 object obj = null; bool objValueEqual = obj.Equals(null); // Behavior 2 object obj = null; Type objType = obj.GetType(); // Behavior 3 string str = (string)null; bool strType = str is string; // Behavior 4 int num = 5; Nullable<int> nullableNum = 5; bool typeEqual = num.GetType() == nullableNum.GetType(); // Behavior 5 Type inType = typeof(int); Type nullableIntType = typeof(Nullable<int>); bool typeEqual = inType == nullableIntType;
static void Main(string[] args)
{
Console.WriteLine(Method(null));
Console.ReadLine();
}
private static string Method(object obj)
{
return "Object parameter";
}
private static string Method(string str)
{
return "String parameter";
} var rounded = Math.Round(1.5); // 2 var rounded = Math.Round(2.5); // 2 var rounded = Math.Round(2.5, MidpointRounding.ToEven); // 2 var rounded = Math.Round(2.5, MidpointRounding.AwayFromZero); // 3 var value = 1.4f; var rounded = Math.Round(value + 0.1f); // 1
public static class Config
{
public static bool ThrowException { get; set; } = true;
}
public class FailingClass
{
static FailingClass()
{
if (Config.ThrowException)
{
throw new InvalidOperationException();
}
}
} try
{
var failedInstance = new FailingClass();
}
catch (TypeInitializationException) { }
Config.ThrowException = false;
var instance = new FailingClass(); public class BaseClass
{
{
public BaseClass()
{
VirtualMethod(1);
}
public virtual int VirtualMethod(int dividend)
{
return dividend / 1;
}
}
public class DerivedClass : BaseClass
{
int divisor;
public DerivedClass()
{
divisor = 1;
}
public override int VirtualMethod(int dividend)
{
return base.VirtualMethod(dividend / divisor);
}
} class Program
{
static void Main(string[] args)
{
var instance = new DerivedClass();
var result = instance.Method();
result = ((BaseClass)instance).Method();
Console.WriteLine(instance + " -> " + result); // Derived Class ... -> Method in BaseClass
Console.ReadLine();
}
}
public class BaseClass
{
public virtual string Method()
{
return "Method in BaseClass";
}
}
public class DerivedClass : BaseClass
{
public override string ToString()
{
return "Derived Class ... ";
}
public new string Method()
{
return "Method in DerivedClass";
}
} class Program
{
static void Main(string[] args)
{
var instance = new DerivedClass();
var result = instance.Method(); // -> Method in DerivedClass
result = ((IInterface)instance).Method(); // -> Method belonging to IInterface
Console.WriteLine(result);
Console.ReadLine();
}
}
public interface IInterface
{
string Method();
}
public class DerivedClass : IInterface
{
public string Method()
{
return "Method in DerivedClass";
}
string IInterface.Method()
{
return "Method belonging to IInterface";
}
} private IEnumerable<int> GetEnumerable(StringBuilder log)
{
using (var test = new Test(log))
{
return Enumerable.Range(1, 5);
}
} var log = new StringBuilder();
foreach (var number in GetEnumerable(log))
{
log.AppendLine($"{number}");
} Created Disposed 1 2 3 4 5
using (var test = new Test(log))
{
foreach (var i in Enumerable.Range(1,5))
{
yield return i;
}
} Created 1 2 3 4 5 Disposed