how to set optional parameter in .net core 6

Hello Mukund,

You can set optional parameters in methods using default parameter values. Check this sample snippet:

public void MyMethod(int requiredParam, string optionalParam = "default value")
{
    // method body
}

In the example above, optionalParam is the optional parameter with a default value of "default value". If the caller doesn't provide a value for optionalParam, the default value will be used.

You can also use named arguments to skip optional parameters and provide values for later parameters in the method signature. 

MyMethod(123); // calls MyMethod with requiredParam = 123, optionalParam = "default value"
MyMethod(456, "custom value"); // calls MyMethod with requiredParam = 456, optionalParam = "custom value"
MyMethod(requiredParam: 789); // calls MyMethod with requiredParam = 789, optionalParam = "default value"

Optional parameters must be the last parameters in the method signature. You can't have a required parameter after an optional parameter.

Hello Mukund,

You can make a URI parameter optional by adding a question mark to the route parameter. 

Example : 

[HttpGet("GetStudent/{studentId?}")]
public IActionResult GetStudent(string studentId) {...

You can refer below link:

https://stackoverflow.com/a/36669280

Thanks

Naimish Makwana

You can make any method with optional parameters by just assigning a default value to that parameter.

just keep in mind optional parameter should always come at the last of all parameters.

public int method(int x=1)
{
  ///to do
}

public int method(int x=1, int y)  // this is wrong and won't work
{
  ///to do
}

public int method(int x, int y=1)  //this is correct
{
  ///to do
}

public int method(string Name, int age=18)  //this is correct
{
  ///to do
}

public int method(int age,string Name="sachin")  //this is correct
{
  ///to do
}

for web app and API you can also use route concept as discussed by others.

Hello Mukund 

Pass optional parameters with route constraints.

[HttpGet("GetById/{id:int?}")]
public Student GetById(int id = 1)
{
    return Student.FirstOrDefault(s => s.Id == id);
}

The default value will be assigned to the method parameter through the model-binding process. The default model-binder in Web API will convert the value “1” to the numeric value 1. 

[HttpGet("GetById/{id:int=1}")]
public Student GetById(int id)
{
    return Student.FirstOrDefault(s => s.Id == id);
}

Thanks

[HttpGet("GetById/{id?}")]

 

example

[HttpGet("GetById/{id:int?}")]
public Product GetById(int id = 1)
{
    var products = Get();
    return products.Where(p => p.Id == id).FirstOrDefault()!;
}