PowerShell自定义类实现未赋值属性隐藏及-Force显示需求

纯PowerShell类无法直接实现「未赋值属性默认隐藏、赋值后显示、-Force强制显示」的逻辑，因此用C#通过Add-Type来实现，同时保留字符串引用返回Name的行为。

完整代码 #

Add-Type @"
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Management.Automation;

public class Package : ICustomTypeDescriptor {
    public string Name { get; set; }
    public string Latest { get; set; }
    public string Prerelease { get; set; }

    public override string ToString() {
        return this.Name;
    }

    PropertyDescriptorCollection ICustomTypeDescriptor.GetProperties() {
        return GetProperties(false);
    }

    PropertyDescriptorCollection ICustomTypeDescriptor.GetProperties(Attribute[] attributes) {
        bool force = false;
        foreach (Attribute attr in attributes) {
            if (attr is PSPropertyInfoAttribute psAttr && psAttr.Force) {
                force = true;
                break;
            }
        }
        return GetProperties(force);
    }

    private PropertyDescriptorCollection GetProperties(bool force) {
        var props = new List<PropertyDescriptor>();
        props.Add(TypeDescriptor.GetProperties(this)["Name"]);
        props.Add(TypeDescriptor.GetProperties(this)["Latest"]);
        
        if (force || Prerelease != null) {
            props.Add(TypeDescriptor.GetProperties(this)["Prerelease"]);
        }
        return new PropertyDescriptorCollection(props.ToArray());
    }

    // 以下为ICustomTypeDescriptor接口的默认实现，无需修改
    AttributeCollection ICustomTypeDescriptor.GetAttributes() => TypeDescriptor.GetAttributes(this);
    string ICustomTypeDescriptor.GetClassName() => TypeDescriptor.GetClassName(this);
    string ICustomTypeDescriptor.GetComponentName() => TypeDescriptor.GetComponentName(this);
    TypeConverter ICustomTypeDescriptor.GetConverter() => TypeDescriptor.GetConverter(this);
    EventDescriptor ICustomTypeDescriptor.GetDefaultEvent() => TypeDescriptor.GetDefaultEvent(this);
    PropertyDescriptor ICustomTypeDescriptor.GetDefaultProperty() => TypeDescriptor.GetDefaultProperty(this);
    object ICustomTypeDescriptor.GetEditor(Type editorBaseType) => TypeDescriptor.GetEditor(this, editorBaseType);
    EventDescriptorCollection ICustomTypeDescriptor.GetEvents() => TypeDescriptor.GetEvents(this);
    EventDescriptorCollection ICustomTypeDescriptor.GetEvents(Attribute[] attributes) => TypeDescriptor.GetEvents(this, attributes);
    object ICustomTypeDescriptor.GetPropertyOwner(PropertyDescriptor pd) => this;
}
"@

# 测试示例
$test = [Package]::new()
$test.Name = 'Example'
$test.Latest = '0.1'

Write-Host "=== 默认输出（Prerelease未赋值，隐藏） ==="
$test | Format-Table

Write-Host "`n=== 赋值Prerelease后输出（显示属性） ==="
$test.Prerelease = '0.1-beta'
$test | Format-Table

Write-Host "`n=== -Force强制输出（无论赋值状态都显示） ==="
$test.Prerelease = $null
$test | Format-Table -Force

Write-Host "`n=== 字符串引用输出（返回Name） ==="
"$test"

逻辑说明 #

• 通过实现ICustomTypeDescriptor接口，接管属性枚举逻辑：
  • 默认模式下，仅返回Name和Latest属性；当Prerelease被赋值（非null）时，才将其加入属性列表
  • 检测到-Force参数时（通过PSPropertyInfoAttribute.Force标识），强制包含Prerelease属性，无论是否赋值
• 重写ToString()方法，确保字符串插值（如"$test"）时返回Name值
• 其余接口方法使用默认实现，保证对象的常规行为不受影响

内容的提问来源于stack exchange，提问作者Maybe