如何在asp.net c#中将json数据绑定到gridview？

Question

I wanted to display the data from JSON file to the gridview . I've managed to decode the JSON file and I was trying to bind with the gridview .

However, an error pops out.

The error is: Newtonsoft.Json.JsonSerializationException: 'Unexpected JSON token when reading DataTable. Expected StartArray, got StartObject. Path '', line 1, position 1

The JSON code:

{
 "value":{

"Status": 2,
    "AffectedSegments": [
      {

        "Line": "NEL",
        "Direction": "HarbourFront",
        "Stations": "NE9,NE8,NE7,NE6", 
      "MRTShuttleDirection": "HarbourFront"}
      ,
      {
        "Line": "EWL",
        "Direction": "Simei", 
     "Stations": "NE9,NE8,NE7,NE6", 
    "MRTShuttleDirection": "HarbourFront"}],
    "Message": [
      {
        "Content": "0901hrs : NEL "
        "CreatedDate": "2018-03-16 09:01:53"
      }
    ]
  }
}

The code:

    public DataTable jsonDataDiplay()
    {
        StreamReader sr = new StreamReader(Server.MapPath("TrainServiceAlerts.json"));
        string json = sr.ReadToEnd();
        var table = JsonConvert.DeserializeObject<DataTable>(json);
        //DataSet ds = JsonConvert.DeserializeObject<Wrapper>(json).DataSet;
        return table;
    }

The design page:

 <asp:GridView ID="GridView2" runat="server">
     <Columns>
         <asp:BoundField DataField="Line" HeaderText="Line" />
         <asp:BoundField DataField="Direction" HeaderText="Direction" />
          <asp:BoundField DataField="Stations" HeaderText="Stations" />
          <asp:BoundField DataField="MRTShuttleDirection" HeaderText="MRTShuttleDirection" />


     </Columns>
 </asp:GridView>

I'm not sure how to solve the error . Please, help me and advise me! i have added " besides NE. It was there from the start in my json file just tht i didnt copy correctly here.

Thank you in advance!

Answer 1

First of all: Your JSON sample is not valid:

"Message": [
  {
    "Content": "0901hrs : NEL  <- ", is missing 
    "CreatedDate": "2018-03-16 09:01:53"
  }
]

Next problem is the that you can not deserialize your json directly to a datatable. Your data sits deep inside the hierachical structure, so you have to do a bit more work to convert this:

public DataTable jsonDataDiplay()
{
    StreamReader sr = new StreamReader(Server.MapPath("TrainServiceAlerts.json"));
    string json = sr.ReadToEnd();
    dynamic table = JsonConvert.DeserializeObject(json);
    DataTable newTable = new DataTable();
    newTable.Columns.Add("Line", typeof(string));
    newTable.Columns.Add("Direction", typeof(string));
    newTable.Columns.Add("Stations", typeof(string));
    newTable.Columns.Add("MRTShuttleDirection", typeof(string));

    foreach (var row in table.value.AffectedSegments)
    {
        newTable.Rows.Add(row.Line, row.Direction, row.Stations, row.MRTShuttleDirection);
    }
    return newTable;
}

Answer 2

This is a sample code that you need i think.

        //Random json string, No fix number of columns or rows and no fix column name.   
        string myDynamicJSON = "[{'Member ID':'00012','First Name':'Vicki','Last Name':'Jordan','Registered Email':'vicki.j @tacinc.com.au','Mobile':'03 6332 3800','MailSuburb':'','MailState':'','MailPostcode':'','Engagement':'attended an APNA event in the past and ventured onto our online education portal APNA Online Learning','Group':'Non-member'},{'Member ID':'15072','First Name':'Vicki','Last Name':'Jordan','Registered Email':'vicki.j @tacinc.com.au','Mobile':'03 6332 3800','MailSuburb':'','MailState':'','MailPostcode':'','Engagement':'attended an APNA event in the past and ventured onto our online education portal APNA Online Learning','Group':'Non-member'}]";  

        //Using dynamic keyword with JsonConvert.DeserializeObject, here you need to import Newtonsoft.Json  
        dynamic myObject = JsonConvert.DeserializeObject(myDynamicJSON);  

        //Binding gridview from dynamic object   
        grdJSON2Grid.DataSource = myObject;  
        grdJSON2Grid.DataBind();  

        //Using DataTable with JsonConvert.DeserializeObject, here you need to import using System.Data;  
        DataTable myObjectDT = JsonConvert.DeserializeObject<DataTable>(myDynamicJSON);  

        //Binding gridview from dynamic object   
        grdJSON2Grid2.DataSource = myObjectDT;  
        grdJSON2Grid2.DataBind();  

Answer 3

As a start you need to validate your JSON.

I used this site to validate it which gave a pretty decent error message on to where your problem is

https://jsonlint.com/

Error: Parse error on line 20:
...": [{            "Content": "0901hrs : NEL           "
----------------------^
Expecting 'STRING', 'NUMBER', 'NULL', 'TRUE', 'FALSE', '{', '[', got 'undefined'

This should be your starting point on fixing this.

I used the validator and a bit of research and found your issue is the following

        "Content": "0901hrs: NEL",

        "CreatedDate": "2018-03-16 09:01:53"

YOUR json seems to be incorrectly formatted ", adding this sorted validation.

From there i would also recommend using objects in c# for reading this file

to create these objects id suggest using this site

http://json2csharp.com/

this will convert any working json to c# objects which you can then read into

after fixing the issue this is how it will look once you have the objects

public class AffectedSegment
{
    public string Line { get; set; }
    public string Direction { get; set; }
    public string Stations { get; set; }
    public string MRTShuttleDirection { get; set; }
}

public class Message
{
    public string Content { get; set; }
    public string CreatedDate { get; set; }
}

public class Value
{
    public int Status { get; set; }
    public List<AffectedSegment> AffectedSegments { get; set; }
    public List<Message> Message { get; set; }
}

public class RootObject
{
    public Value value { get; set; }
}

From here you should be able to read the json into rootobject

 StreamReader sr = new StreamReader(Server.MapPath("TrainServiceAlerts.json"));
        string json = sr.ReadToEnd();
        var table = JsonConvert.DeserializeObject<RootObject>(json);

and then to bind the item to the grid simply do this

MyGridView.DataSource = RootObject
MyGridView.DataBind()

Answer 4

first of all your json is not well formed, at least in the question, i can't edit it as it is only missing a ", at line 21. Now to get to your problem, DeserializeObject<>() can't chew everything you throw at it, most of the times you would create a standalone class and pass that as the type, but in your use case, I can tell that you want to display the first array so you can get it with this:

var jsonLinq = JObject.Parse(json);
        // Find the first array using Linq
        var srcArray = jsonLinq.Descendants().Where(d => d is JArray).First();
        var trgArray = new JArray();
        foreach (JObject row in srcArray.Children<JObject>())
        {
            var cleanRow = new JObject();
            foreach (JProperty column in row.Properties())
            {
                // Only include JValue types
                if (column.Value is JValue)
                {
                    cleanRow.Add(column.Name, column.Value);
                }
            }
            trgArray.Add(cleanRow);
        }
        return JsonConvert.DeserializeObject<DataTable>(trgArray.ToString());

Answer 5

NewtonSoft was expecting the first thing it finds in the json, to be an array, not a single object.

Expecting something like:

  [ <-- ARRAY STARTS
    {"a":"a"},
    {"a":"b"}
  ]

If your json will always look like what you posted, and it's actually only a small sub-part of it that you want to break down to a datatable, you'll need to dig that out first

Alternatively, you can use some service like quicktype.io to create a set of classes that represent your json, so you can parse it into those classes, and use that as your datasource