在.Net中执行js

在.Net中执行js

利用Noesis.Javascript开源组件可以做到在.net中执行js脚本，同时js脚本也能调用C#函数。这个组件的获得方式：在NuGet中输入搜索"Noesis"就能找到。

我们来做个搜索功能：用户能够在textbox中输入js脚本来筛选list记录，界面如下：

然后，click filter button后的UI：

看，筛选出来了，代码如下（js能调C#写的UserInfo类的各个属性）

public class UserInfo
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public int Age { get; set; }
        public override string ToString()
        {
            return string.Format("{0}, {1}: {2}", FirstName, LastName, Age);
        }
    }
 
private void btnSearch_Click(object sender, EventArgs e)
        {
            List<UserInfo> users = FilterUsers(txtFilter.Text.Trim());
            lstUsers.DataSource = users;
        }
 
        private List<UserInfo> FilterUsers(string jsFilter)
        {
            List<UserInfo> results = new List<UserInfo>();
            if (jsFilter.Trim().Length == 0)
                return this.users;
 
            try
            {
                using (JavascriptContext context = new JavascriptContext())
                {
                    foreach (UserInfo user in this.users)
                    {
                        context.SetParameter("user", user);
                        context.SetParameter("isInclude", false);
                        string js = string.Format(@"
                                                if({0})
                                                    isInclude=true;
                                                else
                                                    isInclude=false;", jsFilter);
                        context.Run(js);
                        bool isInclude = (bool)context.GetParameter("isInclude");
                        if (isInclude)
                            results.Add(user);
                    }
                }
            }
            catch
            {
                txtFilter.Focus();
                txtFilter.SelectAll();
                return this.users;
            }
 
            return results;
        }

我们来看看效率：

private void btnTest_Click(object sender, EventArgs e)
        {
            using (JavascriptContext context = new JavascriptContext())
            {
                Stopwatch sw = new Stopwatch();
                sw.Start();
                int i=1000000;
                while(i-- > 0)
                {
                    context.SetParameter("ii", 1);
                    context.SetParameter("jj", 2);
                    context.SetParameter("sum", 0);
                    string js = string.Format(@"sum=ii+jj;");
                    context.Run(js);
                    int sum = (int)context.GetParameter("sum");
                }
                sw.Stop();
 
                long useJS_Total = sw.ElapsedMilliseconds;
                float useJS_Average = ((float)sw.ElapsedMilliseconds) / 1000000;
 
                sw.Reset();
                sw.Start();
                i = 1000000;
                while (i-- > 0)
                {
                    int ii = 1;
                    int jj = 2;
                    int sum = 0;
                    sum = ii + jj;
                }
                sw.Stop();
 
                long nouseJS_Total = sw.ElapsedMilliseconds;
                float nouseJS_Average = ((float)sw.ElapsedMilliseconds) / 1000000;
 
                string msg = "";
                msg += string.Format("useJS_Total: {0}\r\n", useJS_Total);
                msg += string.Format("useJS_Average: {0}\r\n\r\n\r\n", useJS_Average);
                msg += string.Format("nouseJS_Total: {0}\r\n", nouseJS_Total);
                msg += string.Format("nouseJS_Average: {0}\r\n\r\n\r\n", nouseJS_Average);
 
                MessageBox.Show(msg);
            }
        }

结果（上面的是通过js引擎计算的时间、下面的是纯C#计算时间，悲剧啊）：

结论：

1. 这个Noesis.Javascript只适用于性能要求不高的场合
2. 高性能的要看Lua