如何从 ASP.NET 页面返回 JSON 值

Question

我正在使用 asp.net ajax JSON 创建简单的 crud 系统，我创建了函数 get all 以从 all_data.aspx 页面检索值作为 JSON 类型。但我无法检索数据。到目前为止，我尝试了以下内容

表格设计

 <table id="tbl-category" class="table table-responsive table-bordered" cellspacing="0" width="100%">              
                        <thead>
                        <tr>
                            <th></th>
                            <th></th>
                            <th></th>
                            <th></th>
                        </tr>
                    </table>

ajex 函数

function get_all() {
                    $('#tbl-category').dataTable().fnDestroy();
                    $.ajax({
                        url: 'all_data.aspx',
                        type: "GET",
                        dataType: "JSON",
                        success: function (data) {
                            $('#tbl-category').dataTable({
                                "aaData": data,
                                "scrollX": true,
                                "aoColumns": [
                                    { "sTitle": "fname", "mData": "fname" },
                                   { "sTitle": "age", "mData": "age" },

                                    {
                                        "sTitle": "Edit",
                                        "mData": "id",
                                        "render": function (mData, type, row, meta) {
                                            return '<button class="btn btn-xs btn-success" onclick="get_category_details(' + mData + ')">Edit</button>';
                                        }
                                    },
                                    {
                                        "sTitle": "Delete",
                                        "mData": "id",
                                        "render": function (mData, type, row, meta) {
                                            return '<button class="btn btn-xs btn-primary" onclick="RemoveCategory(' + mData + ')">Delete</button>';

                                        }
                                    }

                                ]

                            });

                    },

记录表只包含名字，年龄列在这里如何将此列设置为 JSON 类型我不知道这样做请一些帮助我做到这一点我附在下面我累了到目前为止

**all_data.aspx*

    string sql = "select * from records";
    SqlCommand cmd = new SqlCommand(sql, con);
    con.Open();
    cmd.ExecuteNonQuery();
    DataTable dt = new DataTable();
    SqlDataAdapter da = new SqlDataAdapter();
     da.Fill(dt);

    string sql = "{\"fname\":\"fname\",\"age\":\"age\"}";
    Response.Clear();
    Response.ContentType = "application/json; charset=utf-8";
    Response.Write(json);
    Response.End();

Answer 1

安装using Newtonsoft.Json;。如何安装Newtonsoft.Json

创建一个类：

public class Employee
{
  public string fname {get; set;}
  public int age {get; set;}
}

在方法中：

public string GetEmployees()
{
   string sql = "select * from records";
   SqlCommand cmd = new SqlCommand(sql, con);
   con.Open();
   cmd.ExecuteNonQuery();
   DataTable dt = new DataTable();
   SqlDataAdapter da = new SqlDataAdapter();
   da.Fill(dt);
   List<Employee> employees = new List<Employee>();

   employees = dt.AsEnumerable()
           .Select(x => new Employee()
            {
              fname = x.Field<string>("fname"),
              age = x.Field<int>("age"),
            }).ToList();

   return JsonConvert.SerializeObject(employees);
}

如果您从 C# 方法获取正确的数据，则附加数据，例如：

$.ajax({
 type: "GET",
 url: "https://jsonplaceholder.typicode.com/todos/1",
 success: function(res) {
  $.each(res, function(i, data) {
   $("table.table").append("<tr><td>" + res.userId + "</td><td>" + res.title + "</td></tr>");
  })
 },
 error: function(xhr, status, errorThrown) {
  alert("An error occered, " + errorThrown);
 }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<table id="tbl-category" class="table table-responsive table-bordered" cellspacing="0" width="100%">
   <thead>
      <tr>
         <th>Id</th>
         <th>Name</th>
      </tr>
</table>