How to use dynamic in C# and application scenarios

introduction

In C# programming, the dynamic type is a very special type. It does not perform type checking at compile time, but only performs type parsing at runtime. Dynamic types can improve code flexibility in many cases, but also bring some potential risks. This article will explain in detail the usage methods, advantages and disadvantages of dynamic and some practical application scenarios.

1. What is the dynamic type?

In C#, dynamic types are introduced in .NET Framework 4.0, allowing type checking to be bypassed at compile time, allowing objects with uncertain types to be handled at runtime. dynamic enables you to use some types that are unknown at compile time without explicit type conversion or processing.

2. How dynamic works

When you use dynamic type, the compiler does not statically type check it. Instead, all type checking is performed at runtime. This is because the actual type of the dynamic type is not determined until the program is run.

Sample code:

dynamic example = 10; // The type of example is int(example); // Output 10
example = "Hello, world!"; // The type of example is now string(example); // Output Hello, world!
example = new { Name = "John", Age = 30 }; // The type of example is now an anonymous type(); // Output John

In this example, the type of example changes in different contexts without explicitly declaring its type.

3. Use of dynamic type

1. Declare dynamic type variables

Declaring dynamic type variables is very simple, as follows:

dynamic value = 10;

2. Features of dynamic type(1) Type checking is performed at runtime, not at compile time.

(2) The dynamic type can be assigned a value to any type of object.

(3) The dynamic type can call any method, and even if the method does not exist, the compiler will not report an error.

3. Dynamic type example

Here is an example of the dynamic type:

class Program
{
    static void Main(string[] args)
    {
        dynamic a = 10;
        dynamic b = "Hello World";
        dynamic c = new { Name = "Zhang San", Age = 20 };

        // Output: 10        (a);

        // Output: Hello World        (b);

        // Output: Zhang San        ();

        // Output: 20        ();

        // Call a non-existent method, no error will be reported during compilation, and exceptions will be thrown during runtime        // ();
    }
}

4. Scenarios using dynamic

The dynamic type can be used in the following scenarios:

Interaction with COM components: When you need to interact with COM components, dynamic types are usually used because the interface of COM objects does not always get sufficient type information when compiled.
Handling dynamic data: For example, when you process JSON data, the structure of the data may be uncertain. In this case, using dynamic can make the code more flexible.
Reflection and dynamic calls: dynamic can simplify the code when you need to call methods or access properties dynamically. For example, when using dynamic for method calls, you don't need to manually handle Type and MethodInfo.

Example 1: Interacting with JSON data

using System;
using ;

public class Program
{
    public static void Main()
    {
        string json = "{ 'Name': 'Alice', 'Age': 25 }";
        dynamic data = &lt;dynamic&gt;(json);

        (); // Output Alice        ();  // Output 25    }
}

In this example, dynamic makes it easier to access properties of JSON data.

Example 2: Calling dynamic methods

using System;

public class Program
{
    public static void Main()
    {
        dynamic calculator = new Calculator();
        ((5, 10)); // Output 15    }
}

public class Calculator
{
    public int Add(int a, int b)
    {
        return a + b;
    }
}

In this example, the dynamic type makes method calls more concise, especially when dealing with uncertain objects.

Example 3: Interacting with dynamic language

The dynamic type can easily interact with dynamic languages, as shown below:

dynamic ironPython = ();
dynamic scope = ();
("math");

dynamic math = ("math");
((16)); // Output: 4

5. Pros and cons of dynamic

advantage:

Flexibility: dynamic makes it more flexible to handle objects that cannot be determined at compile time.
Simplified code: Using dynamic can avoid a lot of type conversions and checking code when dealing with dynamic data such as JSON.

shortcoming:

Runtime Error: Since type checking is performed at runtime, it may result in runtime errors that cannot be detected at compile time.
Performance overhead: Dynamic types of operations are slightly slower than static types, because they require more type parsing and method calls at runtime.
Loss of IntelliSense support: When using dynamic types, the IDE's IntelliSense function fails because the compiler cannot provide prompts for the type.

6. Notes on dynamic types

(1) Although the dynamic type will not perform type checking at compile time, an exception will still be thrown at runtime. Therefore, when using dynamic type, pay attention to exception handling.

(2) The dynamic type will affect the readability and maintainability of the code and try to use it if necessary.

(3) The dynamic type may cause performance degradation because it requires the type to be parsed at runtime.

In short, the dynamic type brings great flexibility to C# programming, but be aware of its potential risks when using it. Mastering the dynamic type can make our code more elegant and efficient.

7. Summary

Dynamic types provide great flexibility in C# for handling dynamic data and types, but also bring problems with runtime errors and performance overhead. In actual programming, you need to weigh the benefits and risks of using dynamic and choose the right scenario to use it. For some operations with clear type information, static type checking is still a safer and more efficient choice.

The above is the detailed content of the usage and application scenarios of dynamic in C#. For more information on the use of dynamic in C#, please pay attention to my other related articles!