C# 代码的运行报错 - 上下文不存在名称 File

运行这段 C#代码报错，错误原因定位不了。请问可能是什么原因。

//css_reference Microsoft.VisualBasic.dll;

// 引用必要的命名空间
using System.Windows.Forms;
using System.Collections.Generic;

// Quicker将会调用的函数
public static void Exec(Quicker.Public.IStepContext context)
{
    var model = context.GetVarValue("model");
    List<string> path = (List<string>)(context.GetVarValue("path"));

    foreach (string i in path)
    {
        if (model == "recycleBin")
        {
            if (File.Exists(i))
            {
                Microsoft.VisualBasic.FileIO.FileSystem.DeleteFile(i, Microsoft.VisualBasic.FileIO.UIOption.OnlyErrorDialogs,Microsoft.VisualBasic.FileIO.RecycleOption.SendToRecycleBin);
            }
            else
            {
                Microsoft.VisualBasic.FileIO.FileSystem.DeleteDirectory(i, (Microsoft.VisualBasic.FileIO.DeleteDirectoryOption)Microsoft.VisualBasic.FileIO.RecycleOption.SendToRecycleBin);
            }
        }
        else
        {
            if (File.Exists(i))
            {
                Microsoft.VisualBasic.FileIO.FileSystem.DeleteFile(i);
            }
            else
            {
                Microsoft.VisualBasic.FileIO.FileSystem.DeleteDirectory(i, (Microsoft.VisualBasic.FileIO.DeleteDirectoryOption)Microsoft.VisualBasic.FileIO.RecycleOption.DeletePermanently);
            }
        }
        }
    }