private async Task CopyModelAsCsvToStreamAsync(NameValueCollection requestParameters, Stream responseStream, Func <bool> isCancelled, Func <Task> flushResponseAsync = null)
{
SecurityProviderCache.ValidateCurrentProvider();
string modelName = requestParameters["ModelName"];
string hubName = requestParameters["HubName"];
string filterText = requestParameters["FilterText"];
string sortField = requestParameters["SortField"];
bool sortAscending = requestParameters["SortAscending"].ParseBoolean();
bool showDeleted = requestParameters["ShowDeleted"].ParseBoolean();
string[] parentKeys = requestParameters["ParentKeys"].Split(',');
const int PageSize = 250;
if (string.IsNullOrEmpty(modelName))
{
throw new ArgumentNullException(nameof(modelName), "Cannot download CSV data: no model type name was specified.");
}
if (string.IsNullOrEmpty(hubName))
{
throw new ArgumentNullException(nameof(hubName), "Cannot download CSV data: no hub type name was specified.");
}
Type modelType = AssemblyInfo.FindType(modelName);
if ((object)modelType == null)
{
throw new InvalidOperationException($"Cannot download CSV data: failed to find model type \"{modelName}\" in loaded assemblies.");
}
Type hubType = AssemblyInfo.FindType(hubName);
if ((object)hubType == null)
{
throw new InvalidOperationException($"Cannot download CSV data: failed to find hub type \"{hubName}\" in loaded assemblies.");
}
IRecordOperationsHub hub;
// Record operation tuple defines method name and allowed roles
Tuple <string, string> queryRecordCountOperation;
Tuple <string, string> queryRecordsOperation;
string queryRoles;
try
{
hub = Activator.CreateInstance(hubType) as IRecordOperationsHub;
if ((object)hub == null)
{
throw new SecurityException($"Cannot download CSV data: hub type \"{hubName}\" is not a IRecordOperationsHub, access cannot be validated.");
}
Tuple <string, string>[] recordOperations;
try
{
// Get any authorized query roles as defined in hub records operations for modeled table, default to read allowed for query
recordOperations = hub.RecordOperationsCache.GetRecordOperations(modelType);
if ((object)recordOperations == null)
{
throw new NullReferenceException();
}
}
catch (KeyNotFoundException ex)
{
throw new SecurityException($"Cannot download CSV data: hub type \"{hubName}\" does not define record operations for \"{modelName}\", access cannot be validated.", ex);
}
// Get record operation for querying record count
queryRecordCountOperation = recordOperations[(int)RecordOperation.QueryRecordCount];
if ((object)queryRecordCountOperation == null)
{
throw new NullReferenceException();
}
// Get record operation for querying records
queryRecordsOperation = recordOperations[(int)RecordOperation.QueryRecords];
if ((object)queryRecordsOperation == null)
{
throw new NullReferenceException();
}
// Get any defined role restrictions for record query operation - access to CSV download will based on these roles
queryRoles = string.IsNullOrEmpty(queryRecordsOperation.Item1) ? "*" : queryRecordsOperation.Item2 ?? "*";
}
catch (Exception ex)
{
throw new SecurityException($"Cannot download CSV data: failed to instantiate hub type \"{hubName}\" or access record operations, access cannot be validated.", ex);
}
using (DataContext dataContext = new DataContext())
using (StreamWriter writer = new StreamWriter(responseStream))
{
// Validate current user has access to requested data
if (!dataContext.UserIsInRole(queryRoles))
{
throw new SecurityException($"Cannot download CSV data: access is denied for user \"{Thread.CurrentPrincipal.Identity?.Name ?? "Undefined"}\", minimum required roles = {queryRoles.ToDelimitedString(", ")}.");
}
AdoDataConnection connection = dataContext.Connection;
ITableOperations table = dataContext.Table(modelType);
string[] fieldNames = table.GetFieldNames(false);
Func <Task> flushAsync = async() =>
{
// ReSharper disable once AccessToDisposedClosure
await writer.FlushAsync();
if ((object)flushResponseAsync != null)
{
await flushResponseAsync();
}
};
// Write column headers
await writer.WriteLineAsync(string.Join(",", fieldNames.Select(fieldName => connection.EscapeIdentifier(fieldName, true))));
await flushAsync();
// See if modeled table has a flag field that represents a deleted row
bool hasDeletedField = !string.IsNullOrEmpty(dataContext.GetIsDeletedFlag(modelType));
// Get query operation methods
MethodInfo queryRecordCount = hubType.GetMethod(queryRecordCountOperation.Item1);
MethodInfo queryRecords = hubType.GetMethod(queryRecordsOperation.Item1);
// Setup query parameters
List <object> queryRecordCountParameters = new List <object>();
List <object> queryRecordsParameters = new List <object>();
// Add current show deleted state parameter, if model defines a show deleted field
if (hasDeletedField)
{
queryRecordCountParameters.Add(showDeleted);
}
// Add any parent key restriction parameters
if (parentKeys.Length > 0 && parentKeys[0].Length > 0)
{
queryRecordCountParameters.AddRange(parentKeys);
}
// Add parameters for query records from query record count parameters - they match up to this point
queryRecordsParameters.AddRange(queryRecordCountParameters);
// Add sort field parameter
queryRecordsParameters.Add(sortField);
// Add ascending sort order parameter
queryRecordsParameters.Add(sortAscending);
// Track parameter index for current page to query
int pageParameterIndex = queryRecordsParameters.Count;
// Add page index parameter
queryRecordsParameters.Add(0);
// Add page size parameter
queryRecordsParameters.Add(PageSize);
// Add filter text parameter
queryRecordCountParameters.Add(filterText);
queryRecordsParameters.Add(filterText);
// Read queried records in page sets so there is not a memory burden and long initial query delay on very large data sets
int recordCount = (int)queryRecordCount.Invoke(hub, queryRecordCountParameters.ToArray());
int totalPages = Math.Max((int)Math.Ceiling(recordCount / (double)PageSize), 1);
// Write data pages
for (int page = 0; page < totalPages && !isCancelled(); page++)
{
// Update desired page to query
queryRecordsParameters[pageParameterIndex] = page + 1;
// Query page records
IEnumerable records = queryRecords.Invoke(hub, queryRecordsParameters.ToArray()) as IEnumerable ?? Enumerable.Empty <object>();
int exportCount = 0;
// Export page records
foreach (object record in records)
{
// Periodically check for client cancellation
if (exportCount++ % (PageSize / 4) == 0 && isCancelled())
{
break;
}
await writer.WriteLineAsync(string.Join(",", fieldNames.Select(fieldName => $"\"{table.GetFieldValue(record, fieldName)}\"")));
}
await flushAsync();
}
}
}
