指定另一个参数时未调用 GetDynamicParameters()

Question

我正在 C# 中开发一个 PowerShell cmdlet Get-Foo，它定义了一个 dynamic parameter Bar，只有在指定开关参数 MySwitch 时才会显示。它还有其他参数MyString、MyInt 和MyBool。

当我运行 cmdlet 时，当我指定开关参数 MySwitch 以及 MyString 或 MyInt 时，动态参数 Bar 会很好地显示在选项卡完成中，但当我将它与 @987654332 一起使用时不会@（或任何其他参数类型）。

代码如下：

namespace MyCompany.Cmdlets
{
    [Cmdlet(VerbsCommon.Get, "Foo")]
    public class GetFoo : PSCmdlet, IDynamicParameters
    {
        [Parameter]
        public string MyString { get; set; }

        [Parameter]
        public int MyInt { get; set; }

        [Parameter]
        public bool MyBool { get; set; }

        [Parameter]
        public SwitchParameter MySwitch { get; set; }

        public object GetDynamicParameters()
        {
            if (MySwitch.IsPresent)
            {
                context = new FooParameters();
                return context;
            }

            return null;
        }

        private FooParameters context;

        protected override void ProcessRecord() {}
    }

    public class FooParameters
    {
        [Parameter]
        public string Bar { get; set; }
    }
}

我做错了什么？指定MyBool 参数（或MyObject 参数）时如何显示动态参数？

Answer 1

当使用结构体“SwitchParameter”时，我将其视为处理任何其他布尔值，例如：

if (MySwitchParameter)
{ 
   // la la la other stuff
}

GetDynamicParameters 很棘手，但是，就 Return 而言，您有两个选择 值：返回一个代表您的参数的对象 OR 返回一个 RuntimeDefinedParameterDictionary 对象。想想 RuntimeDefinedParameterDictionary 作为表达参数的“CodeDom-Like”方式。

这里可能会重写您的 Get-Foo Cmdlet，重点是动态参数：

[Cmdlet(VerbsCommon.Get, "Foo",
    SupportsShouldProcess = true
    )]
public class GetFooCommand : PSCmdlet, IDynamicParameters
{
    // First things first: Lets try making a dictionary for our return 
    // value in our implementation of IDynamicParameter's 
    // GetDynamicParameters() method
    private RuntimeDefinedParameterDictionary DynamicParameters;

    [Parameter]
    public string MyString { get; set; }

    [Parameter]
    public int MyInt { get; set; }

    [Parameter]
    // Booleans are not as fun as SwitchParameters, IMHO
    public bool MyBool { get; set; }


    // Remember that SwitchParameter is really just a boolean (sort of), so 
    // it will default to 'false'
    [Parameter]
    public SwitchParameter MySwitch { get; set; }

    public object GetDynamicParameters()
    {
        // You only want this to run when the switch is flipped,
        // so try it this way and see if it works for you
        if (MySwitch)
        {
            // Create the dictionary. We will return this at the end because
            // **** spoiler alert **** it is an object :)
            var runtimeParameterDictionary = new RuntimeDefinedParameterDictionary();


            // Lets make that parameter now. Your example doesn't specify any 
            // additional parameter attributes beyond the required "ParameterAttribute", 
            // so here we create an empty Attribute Collection
            var runtimeParameter = 
            new RuntimeDefinedParameter("Bar", typeof (string), new Collection<Attribute>());

            // With a new Parameter, lets add it to our dictionary. 
            runtimeParameterDictionary.Add("Bar", runtimeParameter);

            // Because we created a field for our dictionary way up top, we can assign it like I
            // illustrate below. This will enable easy, predictable results when we seek to 
            // extract the values from the dictionary at runtime.
            DynamicParameters = runtimeParameterDictionary;


            // Note: You can add as many parameters as you want this way, and that Is 
            // why I recommend it to you now. Coding the parameters as classes outside of the 
            // Cmdlet, and to some extent as embedded Classes,
            // within the Cmdlet Never really worked for me, so I feel your pain/frustration.

            return runtimeParameterDictionary;
        }

        return null; // Guess the user doesn't want that Bar afterall;
    }

    protected override void ProcessRecord()
    {
        // We obviously want to sequester everything we are doing with the dynamic
        // parameters so a good-old-fashioned if.. then.. else... will suffice.
        if (MySwitch)
        {
            // Now we are here at the precipice of this DynamicParameter cmdlet.
            // Here is one way to get the value desired from the dynamic parameter.

            // Simply access it like a dictionary...
            var bar = DynamicParameters["Bar"].Value as string;

            // The reason we can do it this way is because we assigned our
            // beloved value to the local variable "DynmaicParameters"
            // in the GetDynamicParameters() method. We could care less about 
            // the return value, because if the 
            // switch is flipped, "DynamicParameters" will be our new best friend, and
            // it will have everything we need.

            WriteWarning("Your " + bar + " has been forwarded to an automatic voice messaging system ...");
        }


        WriteObject("Cheers was filmed before a live studio audience...");
        WriteObject(MyInvocation.BoundParameters);
    }
}