A custom PowerShell variable provider implementation that evaluates script blocks on inspection

CustomVariableProvider.cs

// Source - https://stackoverflow.com/a/79911456
// Posted by Santiago Squarzon, modified by community. See post 'Timeline' for change history
// Retrieved 2026-03-20, License - CC BY-SA 4.0

using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Management.Automation;
using System.Management.Automation.Provider;

[CmdletProvider(ProviderName, ProviderCapabilities.None)]
public class CustomVariableProvider : ContainerCmdletProvider, IContentCmdletProvider
{
    internal const string ProviderName = "CustomVariable";

    private Dictionary<string, object?>? _variables;

    private Dictionary<string, object?> Variables { get => _variables ??= ((CustomVariableDrive)PSDriveInfo).Variables; }

    private sealed class CustomVariableDrive(PSDriveInfo driveInfo) : PSDriveInfo(driveInfo)
    {
        internal Dictionary<string, object?> Variables { get; } = new(StringComparer.OrdinalIgnoreCase);
    }

    private sealed class CustomVariableHandler(Dictionary<string, object?> vars, string key)
        : IContentReader, IContentWriter
    {
        private bool _read;

        public void Close() { }

        public void Dispose() { }

        public IList Read(long readCount)
        {
            if (_read) return Array.Empty<object>();

            _read = true;
            object? value = vars[key];
            return LanguagePrimitives.ConvertTo<object[]>(
                value switch
                {
                    PSObject { BaseObject: ScriptBlock sb } => sb.InvokeReturnAsIs(),
                    ScriptBlock sb => sb.InvokeReturnAsIs(),
                    _ => value
                });
        }

        public void Seek(long offset, SeekOrigin origin) => throw new NotImplementedException();

        public IList Write(IList content)
        {
            vars[key] = content is { Count: 1 } ? content[0] : content;
            return content;
        }
    }

    private static string NormalizePath(string path) =>
        string.IsNullOrEmpty(path) ? string.Empty : path.Trim('\\', '/');

    protected override PSDriveInfo NewDrive(PSDriveInfo drive) => new CustomVariableDrive(drive);

    private KeyValuePair<string, object?> GetKeyValue(string path) => new(path, Variables[path]);

    protected override bool ItemExists(string path)
    {
        string normalized = NormalizePath(path);
        return string.IsNullOrEmpty(normalized) || Variables.ContainsKey(normalized);
    }

    protected static bool IsItemContainer(string path) => string.IsNullOrEmpty(NormalizePath(path));

    protected override void GetChildItems(string path, bool recurse)
    {
        string normalized = NormalizePath(path);

        if (string.IsNullOrEmpty(normalized))
        {
            foreach (KeyValuePair<string, object?> kvp in Variables)
                WriteItemObject(kvp, kvp.Key, false);

            return;
        }

        WriteItemObject(GetKeyValue(normalized), normalized, false);
    }

    protected override void GetItem(string path)
    {
        string normalized = NormalizePath(path);

        if (string.IsNullOrEmpty(normalized))
        {
            WriteItemObject(Variables, normalized, true);
            return;
        }

        WriteItemObject(GetKeyValue(normalized), normalized, false);
    }

    protected override bool IsValidPath(string path) => true;

    protected override string[] ExpandPath(string path) => [NormalizePath(path)];

    protected override void SetItem(string path, object value) =>
        Variables[NormalizePath(path)] = value;

    protected override void NewItem(string path, string itemTypeName, object newItemValue)
    {
        string normalized = NormalizePath(path);
        // Will throw "An item with the same key has already been added. ..."
        Variables.Add(normalized, newItemValue);
        WriteItemObject(GetKeyValue(normalized), normalized, false);
    }

    public IContentReader GetContentReader(string path) =>
        new CustomVariableHandler(Variables, NormalizePath(path));

    public object? GetContentReaderDynamicParameters(string path) => null;

    public IContentWriter GetContentWriter(string path) =>
        new CustomVariableHandler(Variables, NormalizePath(path));

    public object? GetContentWriterDynamicParameters(string path) => null;

    public void ClearContent(string path)
    {
        string normalized = NormalizePath(path);
        if (Variables.ContainsKey(normalized))
            Variables[normalized] = null;
    }

    public object? ClearContentDynamicParameters(string path) => null;
}

Usage.md

Add-Type -Path .\CustomProvider.cs -WA 0 -IgnoreWarnings -PassThru |
    Import-Module -Assembly { $_.Assembly }

$null = New-PSDrive -Name PS -PSProvider CustomVariable -Root ''

# Can use `Set-Item` or `Set-Content` or `Net-Item` if you choose here...
$PS:Now = { Get-Date }
$PS:Now # Friday, March 20, 2026 12:51:59 PM
Start-Sleep 1
$PS:Now # Friday, March 20, 2026 12:52:00 PM

For more details see https://stackoverflow.com/a/79911456/15339544.