using (StreamReader streamReader = new StreamReader((Stream)cryptoStream))
{
return streamReader.ReadToEnd();
}
Does the using method dispose automatically for streamReader?
Or do I have to manually dispose of streamReader?
The using statement will automatically call Dispose when the variable goes out of scope.
Basically:
using (var x = new StreamReader())
{
return x.ReadToEnd();
}
is equivalent to:
var x = new StreamReader()
try
{
return x.ReadToEnd();
}
finally
{
x.Dispose();
}
Related
I am trying to make a parallel call to Elasticsearch index for multiple queries and aggregate the result, using Parallel.ForEach.
My code:
private static List<SearchResponse<dynamic>> SearchQueryInParallel(string indexName, string lang, string[] eQueries)
{
var result = new List<SearchResponse<dynamic>>();
var exceptions = new ConcurrentQueue<Exception>();
object mutex = new object();
try
{
Parallel.ForEach(eQueries,
() => new SearchResponse<dynamic>()
, (q, loopState, subList) =>
{
var x = LowlevelClient.Search<SearchResponse<dynamic>>(indexName, $"article_{lang}", q);
subList = x;
return subList;
}, subList =>
{
lock (result)
result.Add(subList);
}
);
}
catch (AggregateException ae)
{
foreach (var e in ae.InnerExceptions)
{
exceptions.Enqueue(e);
}
}
if (exceptions.ToList().Any())
{
//there are exceptions, do something with them
//do something?
}
return result;
}
The problem I am facing is that sublist in the above case is long.
It gives me the following error:
Can not convert from SearchResponse to long.
The same thing is working when I used without multithreading, the code is:
var items = new List<dynamic>();
var searchResponse = lowLevelClient.Search<SearchResponse<dynamic>>(elasticIndexName, $"article_{languageCode.ToLowerInvariant()}", query);
foreach (var document in searchResponse.Body.Documents)
{
items.Add(document);
}
Any help, please? If somebody has any other way to achieve the parallel call and aggregating data from returned values would be greatly appreciated.
I have tried to read IMB barcode from an image with the below code snippet, but it always return null. I have also tried with the IMB barcode images in the blackbox testing below, but doesn't work.
https://github.com/micjahn/ZXing.Net/tree/master/Source/test/data/blackbox/imb-1
private static void Decode()
{
Bitmap bitmap = new Bitmap(#"\07.png");
try
{
MemoryStream memoryStream = new MemoryStream();
bitmap.Save(memoryStream, ImageFormat.Bmp);
byte[] byteArray = memoryStream.GetBuffer();
ZXing.LuminanceSource source = new RGBLuminanceSource(byteArray, bitmap.Width, bitmap.Height);
var binarizer = new HybridBinarizer(source);
var binBitmap = new BinaryBitmap(binarizer);
IMBReader imbReader = new IMBReader();
Result str = imbReader.decode(binBitmap);
}
catch { }
}
I have solved this problem by using the below code snippet shared through the below link.
https://github.com/micjahn/ZXing.Net/issues/59
private static void Decode2()
{
var bitmap = new Bitmap(#"\07.png"); // make sure that the file exists at the root level
try
{
var imbReader = new BarcodeReader
{
Options =
{
PossibleFormats = new List<BarcodeFormat> {BarcodeFormat.IMB}
}
};
var result = imbReader.Decode(bitmap);
if (result != null)
System.Console.WriteLine(result.Text);
else
System.Console.WriteLine("nothing found");
}
catch (System.Exception exc)
{
System.Console.WriteLine(exc.ToString());
}
}
I'm developing the service within ASP.NET Boilerplate engine and getting the error from the subject. The nature of the error is not clear, as I inheriting from ApplicationService, as documentation suggests. The code:
namespace MyAbilities.Api.Blob
{
public class BlobService : ApplicationService, IBlobService
{
public readonly IRepository<UserMedia, int> _blobRepository;
public BlobService(IRepository<UserMedia, int> blobRepository)
{
_blobRepository = blobRepository;
}
public async Task<List<BlobDto>> UploadBlobs(HttpContent httpContent)
{
var blobUploadProvider = new BlobStorageUploadProvider();
var list = await httpContent.ReadAsMultipartAsync(blobUploadProvider)
.ContinueWith(task =>
{
if (task.IsFaulted || task.IsCanceled)
{
if (task.Exception != null) throw task.Exception;
}
var provider = task.Result;
return provider.Uploads.ToList();
});
// store blob info in the database
foreach (var blobDto in list)
{
SaveBlobData(blobDto);
}
return list;
}
public void SaveBlobData(BlobDto blobData)
{
UserMedia um = blobData.MapTo<UserMedia>();
_blobRepository.InsertOrUpdateAndGetId(um);
CurrentUnitOfWork.SaveChanges();
}
public async Task<BlobDto> DownloadBlob(int blobId)
{
// TODO: Implement this helper method. It should retrieve blob info
// from the database, based on the blobId. The record should contain the
// blobName, which should be returned as the result of this helper method.
var blobName = GetBlobName(blobId);
if (!String.IsNullOrEmpty(blobName))
{
var container = BlobHelper.GetBlobContainer();
var blob = container.GetBlockBlobReference(blobName);
// Download the blob into a memory stream. Notice that we're not putting the memory
// stream in a using statement. This is because we need the stream to be open for the
// API controller in order for the file to actually be downloadable. The closing and
// disposing of the stream is handled by the Web API framework.
var ms = new MemoryStream();
await blob.DownloadToStreamAsync(ms);
// Strip off any folder structure so the file name is just the file name
var lastPos = blob.Name.LastIndexOf('/');
var fileName = blob.Name.Substring(lastPos + 1, blob.Name.Length - lastPos - 1);
// Build and return the download model with the blob stream and its relevant info
var download = new BlobDto
{
FileName = fileName,
FileUrl = Convert.ToString(blob.Uri),
FileSizeInBytes = blob.Properties.Length,
ContentType = blob.Properties.ContentType
};
return download;
}
// Otherwise
return null;
}
//Retrieve blob info from the database
private string GetBlobName(int blobId)
{
throw new NotImplementedException();
}
}
}
The error appears even before the app flow jumps to 'SaveBlobData' method. Am I missed something?
Hate to answer my own questions, but here it is... after a while, I found out that if UnitOfWorkManager is not available for some reason, I can instantiate it in the code, by initializing IUnitOfWorkManager in the constructor. Then, you can simply use the following construction in your Save method:
using (var unitOfWork = _unitOfWorkManager.Begin())
{
//Save logic...
unitOfWork.Complete();
}
I'm trying to port an Android app with a Realm to Xamarin so it'll be also available for iOS devices. In Android, I have several JSON files with some necessary initial data, e.g. cities.json, and I import it at the beginning with realm.createOrUpdateAllFromJson(Class<E> clazz, InputStream in) method, like this:
private void loadInitialCities(Realm realm) {
InputStream stream = context.getAssets().open("data/cities.json");
realm.createOrUpdateAllFromJson(City.class, stream);
}
I also find this method very useful when retrieving data from a web service in form of JSON.
Now with Xamarin I don't see any equivalent to such method. Is there any method to achieve this? Or at least a workaround/tool to create a RealmObject from a JSON in C#?
I wrote my own extension methods for doing this (yes, I miss the built-in helper methods also).
https://github.com/sushihangover/Realm.Json.Extensions
Here is a basic example of how I do it:
JSON Model:
[
{
"name": "Alabama",
"abbreviation": "AL"
},
{
"name": "Alaska",
"abbreviation": "AK"
},
~~~~
]
Realm Model:
public class State : RealmObject
{
public string name { get; set; }
public string abbreviation { get; set; }
}
Xamarin.Android asset and Newtonsoft Streaming reader:
var config = RealmConfiguration.DefaultConfiguration;
config.SchemaVersion = 1;
using (var theRealm = Realm.GetInstance("StackOverflow.realm"))
using (var assetStream = Assets.Open("States.json"))
using (var streamReader = new StreamReader(assetStream))
using (var jsonTextReader = new JsonTextReader(streamReader))
{
var serializer = new JsonSerializer();
if (!jsonTextReader.Read() || jsonTextReader.TokenType != JsonToken.StartArray)
throw new Exception("Bad Json, start of array missing");
while (jsonTextReader.Read())
{
if (jsonTextReader.TokenType == JsonToken.EndArray)
break;
var state = serializer.Deserialize<State>(jsonTextReader);
theRealm.Write(() =>
{
var realmState = theRealm.CreateObject<State>();
realmState.abbreviation = state.abbreviation;
realmState.name = state.name;
});
}
}
Update: One of my extensions methods:
Extension Method Usage:
using (var theRealm = Realm.GetInstance("StackOverflow.realm"))
using (var assetStream = Assets.Open("States.json"))
{
theRealm.JsonArrayToRealm<State>(assetStream);
}
Extension Method:
Note: This uses AutoMapper to copy RealmObject and avoid reflection, also using Newtonsoft.Json.
public static class RealmDoesJson
{
public static void JsonArrayToRealm<T>(this Realm realm, Stream stream) where T : RealmObject
{
Mapper.Initialize(cfg =>
{
cfg.CreateMap<T, T>();
});
using (var streamReader = new StreamReader(stream))
using (var jsonTextReader = new JsonTextReader(streamReader))
{
var serializer = new JsonSerializer();
if (!jsonTextReader.Read() || jsonTextReader.TokenType != JsonToken.StartArray)
throw new Exception("MALFORMED JSON, Start of Array missing");
while (jsonTextReader.Read())
{
if (jsonTextReader.TokenType == JsonToken.EndArray)
break;
var jsonObject = serializer.Deserialize<T>(jsonTextReader);
realm.Write(() => // inside while loop / single object transaction for memory manangement reasons...
{
var realmObject = realm.CreateObject(typeof(T).Name);
Mapper.Map<T, T>(jsonObject, realmObject);
});
}
}
}
}
using (EntityDataContext amdb = new EntityDataContext(StrConnectionString))
{
if (amdb.DatabaseExists())
{
using (IsolatedStorageFile isoStore = IsolatedStorageFile.GetUserStoreForApplication())
{
if (!isoStore.FileExists(databaseName))
{
copyDatabase = true;
}
else
{
using (IsolatedStorageFileStream databaseStream = isoStore.OpenFile(databaseName, FileMode.Open, FileAccess.Read)) // error here
{
using (Stream db = Application.GetResourceStream(new Uri(databaseName, UriKind.Relative)).Stream)
{
if (databaseStream.Length < db.Length)
copyDatabase = true;
}
}
}
}
}
else
{
//error with the database that has been packaged
}
if (copyDatabase)
new Worker().Copy(databaseName);
}
Check that you precise, in isolated storage access mode parameters, the possibility to write data in there instead of just be able to read.
Did you test with a device?
From what i can tell you're trying to read the database file, while you still have a database connection open. Since the a DataContext locks the database (and thus the file), you're not allowed to read it at the same time.
In order to close the database connection try to close the EntityDataContext object (by calling amdb.Close() or by closing the using statement
Try something like this:
bool shouldCopyDatabase = false;
bool databaseExists = false;
using (EntityDataContext amdb = new EntityDataContext(StrConnectionString))
{
databaseExists = amdb.DatabaseExists();
}
if (databaseExists == true)
{
using (IsolatedStorageFile isoStore = IsolatedStorageFile.GetUserStoreForApplication())
{
if (!isoStore.FileExists(databaseName))
{
copyDatabase = true;
}
else
{
using (IsolatedStorageFileStream databaseStream = isoStore.OpenFile(databaseName, FileMode.Open, FileAccess.Read)) // error here
{
using (Stream db = Application.GetResourceStream(new Uri(databaseName, UriKind.Relative)).Stream)
{
if (databaseStream.Length < db.Length)
copyDatabase = true;
}
}
}
}
}
if (copyDatabase)
new Worker().Copy(databaseName);
By moving the isolated storage access functionality outside of the using (EntityDataContext amdb = new EntityDataContext(StrConnectionString)) scope, you allow the database connection to be closed first.