System.argumentexception: 'no mapping exists from object type newtonsoft.json.linq.jvalue to a known managed provider native type.'

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Hi. im trying to insert data from a JSON Array response that ive gotten as a response. However, i keep getting a "System.ArgumentException: 'No mapping exists from object type Newtonsoft.Json.Linq.JValue to a known managed provider native type.'" error thrown at me. The code that i have is as follows:

private void btnSave_Click(object sender, EventArgs e)
{

string connectionString;
connectionString = @"Data Source=LAPTOP-R0HOA2B6;Initial Catalog=DemoDb;User ID=John;Password=1234";

SqlConnection con = new SqlConnection(connectionString);
//Opens the connection to the database
con.Open();

dynamic jsonObj = JsonConvert.DeserializeObject(txtResponse.Text);

using (SqlCommand cmd = new SqlCommand("Insert into devicedata(device,time,data) VALUES (@device,@time,@data)", con))
{

cmd.Parameters.AddWithValue("@device", jsonObj.data[0].device);
cmd.Parameters.AddWithValue("@time", jsonObj.data[0].time);
cmd.Parameters.AddWithValue("@data", jsonObj.data[0].data);
cmd.ExecuteNonQuery();

}
con.Close();

What I have tried:

Best ive done is that i have tried is googling. Im really really bad at coding. Any/all help is appreciated.

Posted 23-Jul-19 19:20pm

Dan Zainal

Updated 23-Jul-19 21:10pm

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Dominic Burford · Answer 1 · 2019-07-23T21:11:00

You need to use a concrete type that maps the JSON into a class structure that your code can work with. Use something like this (I don't know the exact structure as you haven't specified it, but you get the idea).

C#

[DataContract]
public class Device
{
  [DataMember]
  public int Device {get; set;}

  [DataMember]
  public DateTime Time {get; set;}

  [DataMember]
  public string Data {get; set;}
}

Then in your code, deserialise your response into this instead.

C#

Device jsonObj = JsonConvert.DeserializeObject<Device>(txtResponse.Text);