Controller.Json() returns null

Question

I'm only using ASP.Net and MVC, no other libraries. The code is the following:

//ExpensesController.cs - the controller
public IActionResult getExpenses()
{
    List<ExpensesViewModel> list = new List<ExpensesViewModel>();
    string connectionString = "Data Source=DESKTOP-72RT825;Initial Catalog=AccountingDB;Integrated Security=True;Pooling=False";
    SqlConnection sqlConnection = new SqlConnection(connectionString);
    sqlConnection.Open();
    SqlCommand query = new SqlCommand("Select * from Expenses", sqlConnection);
    try
    {
        SqlDataReader reader;
        reader = query.ExecuteReader();
        while (reader.Read())
        {
            String name = reader.GetValue(0).ToString();
            String value = reader.GetValue(1).ToString();
            String date = reader.GetValue(2).ToString();
            list.Add(new ExpensesViewModel() { Name = name, Date=date, Value = value });
            Debug.Print(name + " " + " " + value);
        }
    }
    catch (SqlException ex)
    {
        Debug.Print(ex.Message);
        return Json(ex.Message);
    }
    JsonResult jsonResult = null;
    try
    {
        jsonResult = Json(list);
    }
    catch(Exception ex)
    {
        Debug.Write(ex.Message);
    }
    return jsonResult;
}


//The View Model
public class ExpensesViewModel
{
    public string Name;
    public string Value;
    public string Date;
}

The data that Json(list) returns is null, even though the list is not, I looked in the debugger, the connection to the DB is good, the data arrives, it is put into the list, but when I try and convert it to Json it fails. I've tried adding elements into the list manually, the Json function still returns null.

What version of mvc are you using?

Serge
– Serge

2021-03-11 12:26:09 +00:00
Commented Mar 11, 2021 at 12:26 — Serge
– Serge, Commented Mar 11, 2021 at 12:26

haldo · Accepted Answer · 2021-03-11 12:42:23Z

2

Change your view model to use properties, not fields:

public class ExpensesViewModel
{
    public string Name { get; set; }
    public string Value { get; set; }
    public string Date { get; set; }
}

The reason is that the default model binder binds to properties with public getters/setters.

answered Mar 11, 2021 at 12:42

haldo

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