Question Mark (?) after session variable reference - What does that mean in C#

Question Mark (?) after session variable reference - What does that mean in C#

In C#, the question mark (?) is the null-conditional operator, which is used to access members of an object or to call methods on an object without throwing a NullReferenceException if the object is null.

When the question mark is used after a session variable reference, it means that the code is checking whether the session variable is null before trying to access a member of the session variable.

For example, consider the following code:

var myObject = HttpContext.Session.GetString("myObjectKey"); if (myObject?.Length > 0) { // Do something with myObject }

In this code, we use the HttpContext.Session.GetString method to get the value of a session variable with the key "myObjectKey". We then use the null-conditional operator (?) to check whether myObject is null before trying to access its Length property. If myObject is null, the condition will evaluate to false and the code inside the if statement will not execute.

This is a more concise way of writing the following code:

var myObject = HttpContext.Session.GetString("myObjectKey"); if (myObject != null && myObject.Length > 0) { // Do something with myObject }

In this code, we check whether myObject is null and has a length greater than zero using the && operator. The null-conditional operator allows us to simplify this code by checking both conditions in a single statement.

Examples

  1. "C# session variable with a question mark (?) at the end"

    • Description: Learn about the meaning of a question mark at the end of a session variable reference in C# and its implications.
    • Code:
      // Assuming session variable retrieval var sessionVariable = HttpContext.Current.Session["YourVariableName"] as SomeType?; // Example usage: if (sessionVariable.HasValue) { // Access the value: sessionVariable.Value }

  2. "C# nullable value types in session variables"

    • Description: Explore the use of nullable value types in session variables and how to handle them.
    • Code:
      // Storing a nullable int in the session int? nullableInt = 42; HttpContext.Current.Session["NullableInt"] = nullableInt; // Retrieving the nullable int from the session int? retrievedValue = HttpContext.Current.Session["NullableInt"] as int?;

  3. "C# session variable null-coalescing operator"

    • Description: Learn how to use the null-coalescing operator with session variables to provide a default value.
    • Code:
      // Assuming session variable retrieval with default value var sessionVariable = HttpContext.Current.Session["YourVariableName"] as SomeType? ?? DefaultValue;

  4. "C# session variable with null conditional operator"

    • Description: Explore the use of the null conditional operator to safely access properties of a session variable.
    • Code:
      // Assuming session variable retrieval and accessing a property var propertyValue = HttpContext.Current.Session["YourVariableName"] as SomeType?.SomeProperty;

  5. "C# session variable nullable reference types"

    • Description: Learn how nullable reference types in C# affect session variable handling.
    • Code:
      // Enabling nullable reference types in C# 8.0 or later #nullable enable // Assuming session variable retrieval with nullable reference type SomeType? sessionVariable = HttpContext.Current.Session["YourVariableName"] as SomeType?;

  6. "C# session variable with nullable types in .NET Core"

    • Description: Explore the usage of nullable types in session variables in .NET Core applications.
    • Code:
      // Assuming session variable retrieval with nullable type in .NET Core SomeType? sessionVariable = HttpContext.Session.Get<SomeType?>("YourVariableName");

  7. "C# session variable with conditional check for null"

    • Description: Learn how to perform a conditional check for null when working with session variables.
    • Code:
      // Assuming session variable retrieval and conditional check for null var sessionVariable = HttpContext.Current.Session["YourVariableName"] as SomeType?; if (sessionVariable != null) { // Access the value: sessionVariable.Value }

  8. "C# session variable with null propagation"

    • Description: Explore the use of null propagation when working with session variables to simplify code.
    • Code:
      // Assuming session variable retrieval with null propagation var propertyValue = HttpContext.Current.Session["YourVariableName"] as SomeType?.SomeProperty;

  9. "C# session variable with null checks for avoiding exceptions"

    • Description: Learn about the importance of null checks to avoid exceptions when working with session variables.
    • Code:
      // Assuming session variable retrieval and avoiding exceptions with null checks var sessionVariable = HttpContext.Current.Session["YourVariableName"] as SomeType?; if (sessionVariable.HasValue) { // Access the value: sessionVariable.Value }

  10. "C# session variable with null handling in .NET 6"

    • Description: Explore improvements in null handling when working with session variables in C#/.NET 6.
    • Code:
      // .NET 6 introduces improved null handling var sessionVariable = HttpContext.Session["YourVariableName"] as SomeType?; // No additional nullable checks needed

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