c# - Linq to SQL 获取多列

Question

我正在开发一个 asp.net MVC Web 应用程序，其中我使用 Linq to Sql 通过 jquery 和 ajax 从数据库获取结果。我的模型有以下代码

 public IEnumerable<string> getComments(long problemID)
        {

            var comment = from c in _objectModel.Comments
                          where c.ProblemID == problemID
                          select new { c.EmpID, c.CommentText, c.Time }.ToString();

            return comment;

        }

我的 Controller 有以下代码

public string GetComments(string problemid)
        {
            List<string> collection =  _discussionRepository.getComments(Convert.ToInt32(problemid)).ToList();
            string comments = null;
            foreach (string item in collection)
            {
                comments += item + "\n";

            }

            return comments; 



        }

在我看来包含

$("#btnPostComment").click(function () {
  var strdata = {
           problemID: $("#problemID").val(),
           commentText: $("#_1").val(),
           empID: $("#empID").val(),
           agree: 0,
           disagree: 0
        };
        $.ajax({
            type: "POST",
            url: "<%= Url.Action("PostComment", "Discussion")  %>",
            data: strdata,
  error: function(msg){
                alert("error" + msg);
            },
            success: function (msg) {
                var id = { problemid :  $("#problemID").val()};
                 $.ajax({
                    type: "GET",
                    url: "<%= Url.Action("GetComments", "Discussion")  %>",
                    data:  id,
                    error: function(msg){
                         alert("error2" + msg);
                    },
                    success: function (msg) {

                        $("#commentdiv").html(msg);
                    }
                    });


            }
        });

我在我的 asp 页面中得到以下结果

{ EmpID = 1，CommentText = sss，时间 = 1/27/2012 2:20:49 AM } { EmpID = 1，CommentText = aaa，时间 = 1/27/2012 2:46:07 AM } { EmpID = 1，CommentText = aaa，时间 = 1/27/2012 2:50:23 AM } { EmpID = 1，CommentText = Munazza，时间 = 1/27/2012 2:58:29 AM } { EmpID = 1, CommentText = Jawad，时间 = 1/27/2012 3:00:51 AM } { EmpID = 1，CommentText = xx，时间 = 1/28/2012 11:56:59 AM } { EmpID = 1，CommentText = ss，时间 = 1/28/2012 12:35:00 PM }

我想获得不带大括号且不带属性的结果，即 1 ss 1/27/2012

问候

Answer 1

问题是您正在调用 ToString关于匿名类型。您现有的Comment模型类包含太多数据？如果没有，您可以使用:

public List<Comment> GetComments(long problemID)
{
    return _objectModel.Comments.Where(c => c.ProblemID == problemID)
                                .ToList(); // Force evaluation
}

然后，您可以更改 Controller 来转换此 List<Comment>转换为 Javascript 可以理解的 AJAX。

如果您真的只想要没有属性的字符串，您可以将原始代码更改为:

public IEnumerable<string> GetComments(long problemID)
{
    var query = from c in _objectModel.Comments
                where c.ProblemID == problemID
                select new { c.EmpID, c.CommentText, c.Time };

    return query.AsEnumerable() // Do the rest locally
                .Select(c => string.Format("{0} {1} {2"}, c.EmpID,
                                           c.CommentText, c.Time));
}

您还应该更改 Controller 代码以使用 String.Join或StringBuilder - 否则，由于重复的字符串连接，您将遇到 O(n²) 问题...