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How to Declare Dynamic Parameters

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This example shows how to define dynamic parameters that are added to the cmdlet at runtime. In this example, the Department parameter is added to the cmdlet whenever the user specifies the Employee switch parameter. For more information about dynamic parameters, see Cmdlet Dynamic Parameters.

To define dynamic parameters

  1. In the cmdlet class declaration, add the System.Management.Automation.Idynamicparameters interface as shown.

    public class SendGreetingCommand : Cmdlet, IDynamicParameters

  2. Call the System.Management.Automation.Idynamicparameters.Getdynamicparameters* method, which returns the object in which the dynamic parameters are defined. In this example, the method is called when the Employee parameter is specified.

    public object GetDynamicParameters()
{
    if (employee)
    {
      context= new SendGreetingCommandDynamicParameters();
      return context;
    }
    return null;
}
private SendGreetingCommandDynamicParameters context;

  3. Declare a class that defines the dynamic parameters to be added. You can use the attributes that you used to declare the static cmdlet parameters to declare the dynamic parameters.

    public class SendGreetingCommandDynamicParameters
{
  [Parameter]
  [ValidateSet ("Marketing", "Sales", "Development")]
  public string Department
  {
    get { return department; }
    set { department = value; }
  }
  private string department;
}

Example

In this example, the Department parameter is added whenever the user specifies the Employee parameter. The Department parameter is an optional parameter, and the ValidateSet attribute is used to specify the allowed arguments.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Management.Automation;     // PowerShell assembly.

namespace SendGreeting
{
  // Declare the cmdlet class that supports the
  // IDynamicParameters interface.
  [Cmdlet(VerbsCommunications.Send, "Greeting")]
  public class SendGreetingCommand : Cmdlet, IDynamicParameters
  {
    // Declare the parameters for the cmdlet.
    [Parameter(Mandatory = true)]
    public string Name
    {
      get { return name; }
      set { name = value; }
    }
    private string name;

    [Parameter]
    [Alias ("FTE")]
    public SwitchParameter Employee
    {
      get { return employee; }
      set { employee = value; }
    }
    private Boolean employee;

    // Implement GetDynamicParameters to
    // retrieve the dynamic parameter.
    public object GetDynamicParameters()
    {
      if (employee)
      {
        context= new SendGreetingCommandDynamicParameters();
        return context;
      }
      return null;
   }
   private SendGreetingCommandDynamicParameters context;

    // Override the ProcessRecord method to process the
    // supplied user name and write out a greeting to
    // the user by calling the WriteObject method.
    protected override void ProcessRecord()
    {
      WriteObject("Hello " + name + "! ");
      if (employee)
      {
        WriteObject("Department: " + context.Department);
      }
    }
  }

  // Define the dynamic parameters to be added
  public class SendGreetingCommandDynamicParameters
  {
    [Parameter]
    [ValidateSet ("Marketing", "Sales", "Development")]
    public string Department
    {
      get { return department; }
      set { department = value; }
    }
    private string department;
  }
}

See Also