C# Default Expression

In C#, the DefaultExpression class specifies a default expression, indicating the default value of a given type. For example, it represents 0 for integers, null for objects, and false for boolean types. The DefaultExpression class is contained within the System.Linq.Expression namespace.

In C#, you can retrieve the default value of a data type by utilizing the Expression class. This class offers a static method named Default(Type) that delivers an object of the DefaultExpression class.

Syntax:

It has the following syntax.

public sealed class DefaultExpression: Expression

In this particular syntax,

• ✅ DefaultExpression: The DefaultExpression is classified as a sealed class, prohibiting inheritance. It is a subclass of the Expression class and is responsible for representing the default value of a specified type within an expression.

Simple C# Default Expression Example

Let's consider a practical example to showcase the default expression in C#.

Example

using System;

using System.Linq.Expressions;

class C# Tutorial

{

    static void Main()

    {

        Expression dexp = Expression.Default(typeof(int));

        Console.WriteLine("Default Expression: " + dexp );

        Console.WriteLine("Type of Expression: " + dexp.Type );

        Console.WriteLine("Node Type: " + dexp.NodeType );

    }

}

Output:

Default Expression: default(Int32)

Type of Expression: System.Int32

Node Type: Default

Explanation:

In the previous illustration, we showcase the implementation of a default expression in C#. Initially, we generate a default expression for the integer type by employing Expression.Default(typeof(int)). By default, an integer's initial value is 0. The representation of the expression appears as default (int32). The Type property reveals the data type of the expression, while the node type property indicates the DefaultExpression node. To conclude, we utilize the Console.WriteLine method to showcase the result.

C# Default Properties

There exist multiple inherent characteristics of the C# default expression. A few of these are outlined below:

C# Default Expression Example using Default Properties

Here, we will use an example to illustrate how default properties are utilized in C#.

Example

using System;

using System.Linq.Expressions;

namespace CSharp

{

    class C# Tutorial

    {

        public static void Main( string[] args = default )

        {

            Expression defaultExpression = Expression.Default(typeof(int));

            show(defaultExpression);

        }

        static void show( Expression defaultExpression )

        {

            // Default expression properties and methods  

            Console.WriteLine("The Instace is " + defaultExpression);

            Console.WriteLine("The Type is " + defaultExpression.Type);

            Console.WriteLine("It can reduce: " + defaultExpression.CanReduce);

            Console.WriteLine("The Instance type is " + defaultExpression.GetType());

            Console.WriteLine("The Node type is " + defaultExpression.NodeType);

        }

    }

}

Output:

The Instace is default(Int32)

The Type is System.Int32

It can reduce: False

The Instance type is System.Linq.Expressions.DefaultExpression

The Node type is Default

Explanation:

In the previous example, we illustrate the application of a default expression in C#. Initially, we define a default expression for the int data type by employing Expression.Default(typeof(int)). The display function is then employed to showcase the attributes and exhibit the default value of int, which is immutable and represents a DefaultExpression object. Lastly, we utilize the Console.WriteLine function to display the result.

C# DefaultExpression Methods

There exist various built-in expressions in the C# programming language, including:

C# Default Expression using Different Methods Example

Next, let's explore a practical example to explain the DefaultExpression function in C#.

Example

using System;

using System.Linq.Expressions;

class C# Tutorial

{

    static void Main()

    {

        DefaultExpression e = Expression.Default(typeof(int));

        Console.WriteLine("Expression: " + e);

        Console.WriteLine("Equals: " + e.Equals(Expression.Default(typeof(int))));

        Console.WriteLine("HashCode: " + e.GetHashCode());

        Console.WriteLine("ToString: " + e.ToString());

        Console.WriteLine("CanReduce: " + e.CanReduce);

        try

        {

            e.Reduce();

        }

        catch (Exception m)

        {

            Console.WriteLine("Reduce Error: " + m.Message);

        }

    }

}

Output:

Expression: default(Int32)

Equals: False

HashCode: 43942917

ToString: default(Int32)

CanReduce: False

Explanation:

In the example provided, we showcase the functionality of the DefaultExpression technique in C#. Initially, we instantiate a variable of the int data type, symbolizing the default value of 0. The script displays the expression as (default(Int32)) and verifies its equivalence with another default expression, resulting in False due to both denoting the same default value. Subsequently, it exhibits the hash code of the expression and confirms that CanReduce is False. Lastly, an attempt to invoke the Reduce method results in an error as DefaultExpression does not facilitate reduction.

Conclusion

In summary, the DefaultExpression serves as a straightforward and effective technique for denoting the default value of various .NET types, like 0 for integers, false for booleans, and null for reference types. This functionality is specified within the System.Linq.Expression namespace, offering a tidy and uniform approach to managing default type values within expression trees.

C# Default Expression FAQs

1) What is the default expression in C#?

In C#, the DefaultExpression class defines a default expression, which displays the default value of a specific type. For instance, it represents 0 for integers, null for objects, and false for boolean values. DefaultExpression is located within the System.Linq.Expression namespace.

The DefaultExpression class is found within the System.Linq.Expressions namespace in C#.

The DefaultExpression class can be found within the System.Linq.Expressions namespace.

3) Explain the CanReduce property in C#?

The CanReduce attribute is inherited from the Expression class, signaling the node's ability to be condensed into a more straightforward form.

4) What is the syntax of DefaultExpression in C#?

It has the following syntax.

public sealed class DefaultExpression: Expression

In this syntax,

The DefaultExpression class is defined as sealed, indicating it cannot be extended through inheritance. This class is a subclass of the Expression class and is responsible for representing the default value associated with a specific type within an expression.

5) What is the node category of a DefaultExpression in C#?

The NodeType attribute of a DefaultExpression consistently provides the ExpressionType.Default value. This denotes that the node signifies a default value expression.