I am using ADO.Net to fill a datatable, the datatable fill method I have put into a separate repository. I inject the repository/interface into a test page model. The page model method "OnPostUpdateAlarmDataTableAsync"needs to call the interface and request the datatable to to be filled. I want to return the result from the task that fills this table, so if the task fails for what ever reasons, I can then inform the user on the UI, I also want to log the details of the error from the page model since this is the calling thread.
Current compile error says "cannot assign void to an implicitly-typed variable" But what ever combination in code changes I try, something never compiles properly. Being able to return the task from an async operation with the relevant info that contains details about the exception is what I want to achieve.
Interface:
public interface IAdoNetRepository
{
Task FillAlarmsDataTable();
}
Repository:
public class AdoNetRepository : IAdoNetRepository
{
public readonly IConfiguration _config;
public AdoNetRepository(IConfiguration config)
{
_config = config;
}
// Used for method below GetUserGroupsData()
public static SqlDataAdapter dataAdapter = new SqlDataAdapter();
public static DataTable alarmDataTable;
public async Task FillAlarmsDataTable()
{
string connectionString = _config.GetConnectionString("Data:DefaultConnection:ConnectionString");
try
{
SqlConnection connection = new SqlConnection(connectionString);
string cmdText1 = "SELECT * FROM [dbo].[Alarms] ORDER BY Name";
// Create a new data adapter based on the specified query.
dataAdapter = new SqlDataAdapter(cmdText1, connection);
// Populate a new data table and bind it to the BindingSource.
alarmDataTable = new DataTable
{
Locale = CultureInfo.InvariantCulture
};
await Task.Run(() => dataAdapter.Fill(alarmDataTable));
//dataAdapter.Fill(alarmDataTable);
return; // Return what ?
}
catch (Exception ex)
{
// Return the task with details of the exception
return; // Return what?
}
}
}
PageModel:
public class TestModel : PageModel
{
private readonly IAdoNetRepository _adoNetRepository;
public TestModel(IAdoNetRepository adoNetRepository)
{
_adoNetRepository = adoNetRepository;
}
public async Task<IActionResult> OnPostUpdateAlarmDataTableAsync()
{
// This gets squiggly line compile error
var result = await _adoNetRepository.FillAlarmsDataTable();
if (!result.Succeeded)
{
// log the exception returned from the task that failed!
}
return new JsonResult(result);
}
}
The comments in the original example shows what you should actually be doing.
you would need to create a model to store the desired information.
Something like
/// <summary>
/// Represents the result of an ADO.Net operation.
/// </summary>
public class AdoNetResult {
private List<Exception> _errors = new List<Exception>();
public bool Succeeded { get; protected set; }
public IEnumerable<Exception> Errors => _errors;
public static AdoNetResult Success { get; } = new AdoNetResult { Succeeded = true };
public static AdoNetResult Failed(params Exception[] errors) {
var result = new AdoNetResult { Succeeded = false };
if (errors != null) {
result._errors.AddRange(errors);
}
return result;
}
}
The interface however would need to be refactored
public interface IAdoNetRepository {
Task<AdoNetResult> FillAlarmsDataTable();
}
and implementation
public async Task<AdoNetResult> FillAlarmsDataTable() {
string connectionString = _config.GetConnectionString("Data:DefaultConnection:ConnectionString");
try {
SqlConnection connection = new SqlConnection(connectionString);
string cmdText1 = "SELECT * FROM [dbo].[Alarms] ORDER BY Name";
// Create a new data adapter based on the specified query.
dataAdapter = new SqlDataAdapter(cmdText1, connection);
// Populate a new data table and bind it to the BindingSource.
alarmDataTable = new DataTable {
Locale = CultureInfo.InvariantCulture
};
await Task.Run(() => dataAdapter.Fill(alarmDataTable));
// Return what ?
return AdoNetResult.Success;
} catch (Exception ex) {
// Return the task with details of the exception
return AdoNetResult.Failed(ex);
}
}
With that done the original code should work as intended
public async Task<IActionResult> OnPostUpdateAlarmDataTableAsync() {
var result = await _adoNetRepository.FillAlarmsDataTable();
if (!result.Succeeded) {
// log the exception returned from the task that failed!
//result.Errors
}
return new JsonResult(result);
}
An alternative would be to let FillAlarmsDataTable
throw any exceptions that it may encounter
public Task FillAlarmsDataTable() {
string connectionString = _config.GetConnectionString("Data:DefaultConnection:ConnectionString");
SqlConnection connection = new SqlConnection(connectionString);
string cmdText1 = "SELECT * FROM [dbo].[Alarms] ORDER BY Name";
// Create a new data adapter based on the specified query.
dataAdapter = new SqlDataAdapter(cmdText1, connection);
// Populate a new data table and bind it to the BindingSource.
alarmDataTable = new DataTable {
Locale = CultureInfo.InvariantCulture
};
return Task.Run(() => dataAdapter.Fill(alarmDataTable));
}
capture (catch) the exception where it is being used and respond accordingly
public async Task<IActionResult> OnPostUpdateAlarmDataTableAsync() {
try {
await _adoNetRepository.FillAlarmsDataTable();
return Ok(); //200 OK
catch(Exception ex) {
//...log the exception returned from the task that failed!
return new ExceptionResult(ex, includeErrorDetail:true);
}
}
Hi Nkosi, thank you so much for your help, this is absolutely excellent :)