Question

我正在尝试使用JSON，当时我正在使用PostMan返回响应这个错误发生了 System.Collections.Generic.List`1 [System.String]“}

    public ActionResult SendVFCode(string Phone_Number)
    {
        var jsonSerialiser = new JavaScriptSerializer();
        string error = "";
        var SearchData ="";

        if (Phone_Number == null)
        {
            error = "Must enter your phone number";
        }
        else if ( (db.PhoneNumbers.Select(x =>x.Id).Count() < 0)
              &&  (db.Assistant.Select(x =>x.Id).Count()) < 0)
        {
            error = "There are no data or your account is not activated";
        }
        else
        {                
            SearchData = db.PhoneNumbers.Include(x => x.Assistant)
            .Where(x => x.PhoneNumber == Phone_Number 
            && x.Assistant.IsActive == true).Select(xx =>xx.PhoneNumber).ToList().ToString();
        }

        json = new
        {
            err = error,
            ResultSearchData = SearchData
        };

        return Content(jsonSerialiser.Serialize(json));
    }

Answer 1

SearchData不是字符串。不要将其声明为字符串，也不要尝试将字符串推入其中。这是一个列表（可能是List<string>类型，也可能是您的电话号码类型）。

var SearchData =""

应该是：

List<string> SearchData;

您的数据库调用应以.ToList()结尾，而不是.ToList().ToString()。

Answer 2

请注意，ToList()后跟ToString()返回列表的标准名称，而不是列表内容，因此，您应使用List<string>来保存结果字符串（列表也必须是先实例化，然后再在if块内使用）。正确的设置应如下所示：

public ActionResult SendVFCode(string Phone_Number)
{
    var jsonSerialiser = new JavaScriptSerializer();
    string error = "";
    var SearchData = new List<string>(); // instantiate list of strings

    var phoneCount = db.PhoneNumbers.Select(x => x.Id).Count();
    var assistantCount = db.Assistant.Select(x => x.Id).Count();

    if (Phone_Number == null)
    {
        error = "Must enter your phone number";
    }
    else if (phoneCount < 0 && assistantCount < 0)
    {
        error = "There are no data or your account is not activated";
    }
    else
    {                
        // assign list from query results
        SearchData = db.PhoneNumbers.Include(x => x.Assistant)
        .Where(x => x.PhoneNumber == Phone_Number && x.Assistant.IsActive == true)
        .Select(xx => xx.PhoneNumber).ToList();
    }

    var json = new
    {
        err = error,
        ResultSearchData = SearchData
    };

    return Content(jsonSerialiser.Serialize(json));
}

System.Collections.Generic.List`1 [System.String]“ JSON错误

2 个答案: