generate 2d barcode vb.net Part II Designing Types in Visual C#.NET

Maker PDF-417 2d barcode in Visual C#.NET Part II Designing Types

Part II Designing Types
Making PDF-417 2d Barcode In Visual C#
Using Barcode creation for VS .NET Control to generate, create PDF 417 image in VS .NET applications.
www.OnBarcode.com
PDF-417 2d Barcode Reader In Visual C#
Using Barcode reader for .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
// Error: conflicts with AType<T1, T2> internal sealed class AType<T3, T4> {} internal sealed class AnotherType { // It is OK to define the following methods: private static void M() {} private static void M<T>() {} private static void M<T1, T2>() {} // Error: conflicts with M<T> that has no constraints private static void M<T>() where T : IComparable<T> {} // Error: conflicts with M<T1, T2> private static void M<T3, T4>() {} }
Bar Code Creator In Visual C#
Using Barcode printer for .NET framework Control to generate, create barcode image in Visual Studio .NET applications.
www.OnBarcode.com
Reading Barcode In Visual C#.NET
Using Barcode decoder for .NET framework Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
When overriding a virtual generic method, the overriding method must specify the same number of type parameters, and these type parameters will inherit the constraints specified on them by the base class s method . In fact, the overriding method is not allowed to specify any constraints on its type parameters at all . However, it can change the names of the type parameters . Similarly, when implementing an interface method, the method must specify the same number of type parameters as the interface method, and these type parameters will inherit the constraints specified on them by the interface s method . Here is an example that demonstrates this rule by using virtual methods:
Printing PDF-417 2d Barcode In .NET Framework
Using Barcode generation for ASP.NET Control to generate, create PDF417 image in ASP.NET applications.
www.OnBarcode.com
Encoding PDF-417 2d Barcode In .NET
Using Barcode printer for .NET framework Control to generate, create PDF 417 image in .NET applications.
www.OnBarcode.com
internal class Base { public virtual void M<T1, T2>() where T1 : struct where T2 : class { } } internal sealed class Derived : Base { public override void M<T3, T4>() where T3 : EventArgs // Error where T4 : class // Error { } }
PDF 417 Drawer In VB.NET
Using Barcode creation for VS .NET Control to generate, create PDF 417 image in Visual Studio .NET applications.
www.OnBarcode.com
Matrix Barcode Generator In C#
Using Barcode encoder for .NET Control to generate, create Matrix 2D Barcode image in .NET framework applications.
www.OnBarcode.com
Attempting to compile the code above causes the compiler to issue the following message: "error CS0460: Constraints for override and explicit interface implementation methods are inherited from the base method so cannot be specified directly." If we remove the two where lines from the Derived class s M<T3, T4> method,
Generating Linear 1D Barcode In C#.NET
Using Barcode printer for .NET Control to generate, create Linear 1D Barcode image in VS .NET applications.
www.OnBarcode.com
Printing USS-128 In C#
Using Barcode creator for VS .NET Control to generate, create EAN / UCC - 13 image in .NET framework applications.
www.OnBarcode.com
the code will compile just fine . Notice that you can change the names of the type parameters (as in the example: from T1 to T3 and T2 to T4); however, you cannot change (or even specify) constraints . Now let s talk about the different kinds of constraints the compiler/CLR allows you to apply to a type parameter . A type parameter can be constrained using a primary constraint, a secondary constraint, and/or a constructor constraint . I ll talk about these three kinds of constraints in the next three sections .
Printing Code 3/9 In Visual C#.NET
Using Barcode encoder for .NET framework Control to generate, create Code 39 Full ASCII image in .NET framework applications.
www.OnBarcode.com
Code 93 Full ASCII Creator In C#
Using Barcode generator for Visual Studio .NET Control to generate, create USS Code 93, USS 93 image in .NET framework applications.
www.OnBarcode.com
12 Generics
Decoding Barcode In .NET
Using Barcode Control SDK for ASP.NET Control to generate, create, read, scan barcode image in ASP.NET applications.
www.OnBarcode.com
Draw UPC Symbol In .NET Framework
Using Barcode generator for Reporting Service Control to generate, create UPC-A image in Reporting Service applications.
www.OnBarcode.com
Primary Constraints
PDF-417 2d Barcode Generation In Java
Using Barcode creation for Java Control to generate, create PDF-417 2d barcode image in Java applications.
www.OnBarcode.com
Drawing Barcode In Visual Studio .NET
Using Barcode creator for VS .NET Control to generate, create barcode image in VS .NET applications.
www.OnBarcode.com
A type parameter can specify zero primary constraints or one primary constraint . A primary constraint can be a reference type that identifies a class that is not sealed . You cannot specify one of the following special reference types: System.Object, System.Array, System.Delegate, System.MulticastDelegate, System.ValueType, System.Enum, or System.Void . When specifying a reference type constraint, you are promising the compiler that a specified type argument will either be of the same type or of a type derived from the constraint type . For example, see the following generic class:
USS Code 39 Maker In None
Using Barcode generation for Font Control to generate, create Code39 image in Font applications.
www.OnBarcode.com
QR Code 2d Barcode Generator In None
Using Barcode creation for Microsoft Excel Control to generate, create Denso QR Bar Code image in Microsoft Excel applications.
www.OnBarcode.com
internal sealed class PrimaryConstraintOfStream<T> where T : Stream { public void M(T stream) { stream.Close();// OK } }
Generating UPC-A Supplement 5 In VB.NET
Using Barcode printer for .NET framework Control to generate, create UPC-A Supplement 2 image in Visual Studio .NET applications.
www.OnBarcode.com
Encode EAN 13 In None
Using Barcode generation for Font Control to generate, create UPC - 13 image in Font applications.
www.OnBarcode.com
In this class definition, the type parameter T has a primary constraint of Stream (defined in the System.IO namespace) . This tells the compiler that code using PrimaryConstraintOfStream must specify a type argument of Stream or a type derived from Stream (such as FileStream) . If a type parameter doesn t specify a primary constraint, System.Object is assumed . However, the C# compiler issues an error message ("error CS0702: Constraint cannot be special class 'object' ") if you explicitly specify System.Object in your source code . There are two special primary constraints: class and struct . The class constraint promises the compiler that a specified type argument will be a reference type . Any class type, interface type, delegate type, or array type satisfies this constraint . For example, see the following generic class:
internal sealed class PrimaryConstraintOfClass<T> where T : class { public void M() { T temp = null;// Allowed because T must be a reference type } }
In this example, setting temp to null is legal because T is known to be a reference type, and all reference type variables can be set to null . If T were unconstrained, the code above would not compile because T could be a value type, and value type variables cannot be set to null . The struct constraint promises the compiler that a specified type argument will be a value type . Any value type, including enumerations, satisfies this constraint . However, the compiler and the CLR treat any System.Nullable<T> value type as a special type, and nullable types do not satisfy this constraint . The reason is because the Nullable<T> type constrains its type parameter to struct, and the CLR wants to prohibit a recursive type such
Copyright © OnBarcode.com . All rights reserved.