缺少命令错误;为Windows 10应用程序创建自定义cordova插件

Question

我尝试使用自定义插件调用C＃类。我使用Cordova创建了一个通用的Windows 10应用程序。这是我的C＃类，名为Echo.cs

using System;
using WPCordovaClassLib.Cordova;
using WPCordovaClassLib.Cordova.Commands;
using WPCordovaClassLib.Cordova.JSON;

public class Echo : BaseCommand
{
    public void echo(string options)
    {
        // all JS callable plugin methods MUST have this signature!
        // public, returning void, 1 argument that is a string

        DispatchCommandResult();
    }
}

当设备准备就绪时，我致电

function onDeviceReady() {
    // Handle the Cordova pause and resume events
    document.addEventListener( 'pause', onPause.bind( this ), false );
    document.addEventListener( 'resume', onResume.bind( this ), false );

    // TODO: Cordova has been loaded. Perform any initialization that requires Cordova here.

    var win = function (result) {
        console.log("Success");
        console.log(result);
    };
    var fail = function (result) {
        console.log("Fail");
        console.log(result);
    };

    cordova.exec(win, fail, "Echo", "echo", ["input string"]);
};

但总是因此错误而失败;缺少命令错误。它似乎无法找到班级？

https://cordova.apache.org/docs/en/latest/guide/platforms/wp8/plugin.html

没有帮助。我可能错过了什么？我已尝试将.cs文件放在不同的项目（属于同一解决方案），插件文件夹，根文件夹等中。