为什么在 Context.Response.Write() 中显示错误

Question

我是 ASP.Net 开发的新手，在将数据从 webService 发送到 webform 时遇到问题。我正在使用 JSON 方法，但在下面的代码行中我遇到了问题。编译器显示此错误消息。

"错误 3 类、结构或接口成员中的无效标记 '(' 声明

谁能告诉我是什么问题？

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Web.Script.Serialization;
using System.Configuration;
using System.Data.SqlClient;
using System.Data;
using System.Runtime.Remoting.Contexts;
using System.Runtime.Remoting;

/// <summary>
/// Summary description for GetStudent
/// </summary>
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
// To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. 
[System.Web.Script.Services.ScriptService]
public class GetStudent : System.Web.Services.WebService {

    [WebMethod]
    public GetStudent () {

        //Uncomment the following line if using designed components 
        //InitializeComponent(); 
    }

    [WebMethod]
    public void GetStudent () {
        SqlConnection con = new SqlConnection("Data Source=(LocalDB)\\v11.0;AttachDbFilename='C:\\Users\\Abdul Basit Mehmood\\Documents\\Visual Studio 2012\\WebSites\\WebSite1\\App_Data\\Database.mdf';Integrated Security= True");
        List<StudentsList> stu = new List<StudentsList>();
        con.Open();
        SqlCommand cmd = con.CreateCommand();
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = "Select * From Student";
        SqlDataReader DR = cmd.ExecuteReader();
        while (DR.Read())
        {
            StudentsList student = new StudentsList();
            student.Id = Convert.ToInt32(DR["Id"]);
            student.name = DR["name"].ToString();
            student.fname = DR["fname"].ToString();
            student.email = DR["email"].ToString();
            student.contact = DR["contact"].ToString();
            student.Pname = DR["Pname"].ToString();
            student.Cname = DR["Cname"].ToString();
            StudentsList.Add(student);

        }

        JavaScriptSerializer js = new JavaScriptSerializer(StudentsList());
        Context.Response.Write(js.Serializ(StudentsList));
    }


}

Answer 1

以下是您需要修复 GetStudent 方法的方法 -

    [WebMethod]
    public void GetStudent () {
        SqlConnection con = new SqlConnection("Data Source=(LocalDB)\\v11.0;AttachDbFilename='C:\\Users\\Abdul Basit Mehmood\\Documents\\Visual Studio 2012\\WebSites\\WebSite1\\App_Data\\Database.mdf';Integrated Security= True");
        List<StudentsList> stu = new List<StudentsList>();
        con.Open();
        SqlCommand cmd = con.CreateCommand();
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = "Select * From Student";
        SqlDataReader DR = cmd.ExecuteReader();
        while (DR.Read())
        {
            StudentsList student = new StudentsList();
            student.Id = Convert.ToInt32(DR["Id"]);
            student.name = DR["name"].ToString();
            student.fname = DR["fname"].ToString();
            student.email = DR["email"].ToString();
            student.contact = DR["contact"].ToString();
            student.Pname = DR["Pname"].ToString();
            student.Cname = DR["Cname"].ToString();
            stu.Add(student); //Changed line: Changed variable name to stu which is the list variable declared earlier.

        }
    JavaScriptSerializer js = new JavaScriptSerializer(); //changed line : Removed the invalid parameter to the constructor of JavaScriptSerializer class
    Context.Response.Write(js.Serializ(stu)); //changed line : Used the correct stu list variable declared at the starting of the method.
}

注意：在命名班级时请格外小心。您的 StudentList 实体不是一个列表，而是一个具有各种属性的单个学生实体，例如 Id、name、fname 等。请考虑将其重命名为 Student。

为了验证您没有从数据库中获取任何无效字符，请先尝试运行以下代码是否正常？

class Program
{
        static void Main(string[] args)
        {
            List<StudentsList> stu = new List<StudentsList>();

            StudentsList student = new StudentsList();
            student.name = "Abdul Basit Mehmood";
            student.fname = "Abdul";
            stu.Add(student); 
            JavaScriptSerializer js = new JavaScriptSerializer(); 
            var serializedValue = js.Serialize(stu); 
         }
}

class StudentsList
{
    public string name;
    public string fname;
}

serializedValue 变量应该在快速观察窗口中显示一个有效的 JSON 字符串，如下所示：