I am working on a windows service in c#, and perhaps I might use the same methods in my web application if it works. The main service is using a sqlconnection that is used for itself, retrieved from app.config using ConfigurationManager, and it creates a few threads of different types, to run several tasks. Each of these threads has its own connection (stored in class property).
public partial class MainService : ServiceBase{
private static string SQLConnStr;
protected static SqlConnection SQLConn;
}
class OtherClass{
private sqlconnection sqlconn;
private string connstr;
}
The part that I am stuck with, is that, when I create another object type, I need that object to be able to access the DB using OtherClass' connection. This new object is created and called in OtherClass for processing later on.
Is it possible to re-use the sql connection from OtherClass?
Is it safe and secure to make the sql connection string as public static?
Is the design I am using not good?
pass it to OtherClass constructor ?
details with example:
public partial class MainService : ServiceBase{
private string SQLConnStr;
}
class OtherClass{
private string connstr;
public OtherClass(string _connstr) { this.connstr = _connstr; }
public foo() { using(var conn = new SqlConnection(connstr) { ... } }
}
Creating new SqlConnection each time is fine in .NET since there is connection pool.
You should use the respective configuration mechanism. For applications/windows services this would bee the app.config file, for web applications it would be the web.config file and for DLLs, the settings should be copied from the DLL's app.config to the application's app.config/web.config as described here many times (DLLs don't read their config files, so the settings need to go into the application's config file).
That being said: Use the settings designer in Visual Studio to simply add a new connection string setting. If necessary, add it to other projects, too.
To use the connection string from class within the same project, you can then simply use Settings.Default.MyConnectionString assuming that the setting is named MyConnectionString.
Another exception for DLLs: Some DLLs don't need their own settings, but they need to access a database. In that case you could pass the connection string or even an SqlConnection to the function that requires database access.
There is a distinction between connection*string* and the connection itself. For the connectionstring (describing where you should connect to), you can store that in a config file so youu can easily change it.
The connection itself that is used to communicate with the database must be opened and closed. When you use datareaders, you can't usually use the same connection for simultaneous commands.
It is best to open a new connection as late as possible and close it as soon as possible. Let the built-in connectionpooling do it's thing to optimize the real connections.
I like your answers, but mine is the case of bad design, after looking into it a while. So I decided to create a public static query function in the MainService:
public static void qQuery(string querystr){
using(sqlconnection conn = new sqlconnection(sqlconnstr){
.....
}
}
sqlconnstr is a private string in MainService which is initialized when the service starts.
I hope it is safe and secure way of doing it...
I am writing a C# .NET 4.5-based Windows Forms application.
I'd like to set a flag (Boolean) in one of the classes (probably the main Form's class) that defines whether the app is running in Production of Debug mode. I will use this flag to control various actions of the app, including GUI-based actions as well as which connection string to use.
I don't have a problem with the GUI-based stuff because the flag is defined in the main Form's class, but I'm having a problem with the connection string. There is a separate class for DB access, which basically just defines a constant like this:
namespace MyApp
{
class DatabaseInterface
{
public static string MyConnectionString = "Data Source=server;Initial Catalog=db";
}
}
I'd like to change the connection string (really just the "server") depending on that production/debug flag. I do NOT want to put an if/then/else in every place where the connection string is used (to toggle between debug and production strings), but would like a single named connection string that can be used throughout the app. I'd also prefer to NOT have to instantiate a DatabaseInterface object (I know I could dynamically change this in the "get" definition of a public property of the DatabaseInterface class).
Is there a way to do this?
If you want to do this based on a flag and don't want the if everywhere, I'd suggest that you use a simple getter like this :
namespace MyApp
{
class DatabaseInterface
{
public static string getConnectionString()
{
return myFlag ? "Data Source=server;Initial Catalog=db" : "AnotherString";
}
}
}
I have an integration test LoadFile_DataLoaded_Successfully(). And I want to refactor it to the unit test for breaking dependency with filesytem.
P.S. I am new in TDD:
Here are my production class :
public class LocalizationData
{
private bool IsValidFileName(string fileName)
{
if (fileName.ToLower().EndsWith("xml"))
{
return true;
}
return false;
}
public XmlDataProvider LoadFile(string fileName)
{
if (IsValidFileName(fileName))
{
XmlDataProvider provider =
new XmlDataProvider
{
IsAsynchronous = false,
Source = new Uri(fileName, UriKind.Absolute)
};
return provider;
}
return null;
}
}
and my test class (Nunit)
[TestFixture]
class LocalizationDataTest
{
[Test]
public void LoadFile_DataLoaded_Successfully()
{
var data = new LocalizationData();
string fileName = "d:/azeri.xml";
XmlDataProvider result = data.LoadFile(fileName);
Assert.IsNotNull(result);
Assert.That(result.Document, Is.Not.Null);
}
}
Any idea how to refactor it to break filesystem dependency
What you're missing here is inversion of control. For instance, you can introduce the dependency injection principle into your code:
public interface IXmlDataProviderFactory
{
XmlDataProvider Create(string fileName);
}
public class LocalizationData
{
private IXmlDataProviderFactory factory;
public LocalizationData(IXmlDataProviderFactory factory)
{
this.factory = factory;
}
private bool IsValidFileName(string fileName)
{
return fileName.ToLower().EndsWith("xml");
}
public XmlDataProvider LoadFile(string fileName)
{
if (IsValidFileName(fileName))
{
XmlDataProvider provider = this.factory.Create(fileName);
provider.IsAsynchronous = false;
return provider;
}
return null;
}
}
In the code above the creation of the XmlDataProvider is abstracted away using an IXmlDataProviderFactory interface. An implementation of that interface can be supplied in the constructor of the LocalizationData. You can now write your unit test as follows:
[Test]
public void LoadFile_DataLoaded_Succefully()
{
// Arrange
var expectedProvider = new XmlDataProvider();
string validFileName = CreateValidFileName();
var data = CreateNewLocalizationData(expectedProvider);
// Act
var actualProvider = data.LoadFile(validFileName);
// Assert
Assert.AreEqual(expectedProvider, actualProvider);
}
private static LocalizationData CreateNewLocalizationData(
XmlDataProvider expectedProvider)
{
return new LocalizationData(FakeXmlDataProviderFactory()
{
ProviderToReturn = expectedProvider
});
}
private static string CreateValidFileName()
{
return "d:/azeri.xml";
}
The FakeXmlDataProviderFactory looks like this:
class FakeXmlDataProviderFactory : IXmlDataProviderFactory
{
public XmlDataProvider ProviderToReturn { get; set; }
public XmlDataProvider Create(string fileName)
{
return this.ProviderToReturn;
}
}
Now in your test environment you can (and probably should) always create the class under test manually. However, you want to abstract the creation away in factory methods to prevent you having to change many tests when the class under test changes.
In your production environment however, it can become very cumbersome very soon when you manually have to create the class. Especially when it contains many dependencies. This is where IoC / DI frameworks shine. They can help you with this. For instance, when you want to use the LocalizationData in your production code, you might write code like this:
var localizer = ServiceLocator.Current.GetInstance<LocalizationData>();
var data = data.LoadFile(fileName);
Note that I'm using the Common Service Locator as an example here.
The framework will take care of the creation of that instance for you. Using such a dependency injection framework however, you will have to let the framework know which 'services' your application needs. For instance, when I use the Simple Service Locator library as an example (shameless plug that is), your configuration might look like this:
var container = new SimpleServiceLocator();
container.RegisterSingle<IXmlDataProviderFactory>(
new ProductionXmlDataProviderFactory());
ServiceLocator.SetLocatorProvider(() => container);
This code will usually go in the startup path of your application. Of course the only missing piece of the puzzle is the actual ProductionXmlDataProviderFactory class. Here is it:
class ProductionXmlDataProviderFactory : IXmlDataProviderFactory
{
public XmlDataProvider Create(string fileName)
{
return new XmlDataProvider
{
Source = new Uri(fileName, UriKind.Absolute)
};
}
}
Please also not that you will probably don't want to new up your LocalizationData in your production code yourself, because this class is probably used by other classes that depend on this type. What you would normally do is ask the framework to create the top most class for you (for instance the command that implements a complete use case) and execute it.
I hope this helps.
The problem here is that you are not doing TDD. You wrote the production code first, and now you want to test it.
Erase all that code and start again. Write a test first, and then write the code that passes that test. Then write the next test, etc.
What is your goal? Given a string that ends in "xml" (why not ".xml"?) you want an XML data provider based upon a file whose name is that string. Is that your goal?
The first tests would be the degenerate case. Given a string like "name_with_wrong_ending" your function should fail. How should it fail? Should it return null? Or should it throw an exception? You get to think about this and decide in your test. Then you make the test pass.
Now, what about a string like this: "test_file.xml" but in the case where no such file exists? What do you want the function to do in that case? Should it return null? Should it throw an exception?
The simplest way to test this, of course, is to actually run the code in a directory that does not have that file in it. However, if you'd rather write the test so that it does not use the file system (a wise choice) then you need to be able to ask the question "Does this file exist", and then your test needs to force the answer to be "false".
You can do that by creating a new method in your class named "isFilePresent" or "doesFileExist". Your test can override that function to return 'false'. And now you can test that your 'LoadFile' function works correctly when the file doesn't exist.
Of course now you'll have to test that the normal implementation of "isFilePresent" works correctly. And for that you'll have to use the real file system. However, you can keep file system tests out of your LocalizationData tests by creating a new class named FileSystem and moving your 'isFilePresent' method into that new class. Then your LocalizationData test can create a derivative of that new FileSystem class and override 'isFilePresent' to return false.
You still have to test the regular implementation of FileSystem, but that's in a different set of tests, that only get run once.
OK, what's the next test? What does your 'loadFile' function do when the file does exist, but does not contain valid xml? Should it do anything? Or is that a problem for the client? You decide. But if you decide to check it, you can use the same strategy as before. Make a function named isValidXML and have the test override it to return false.
Finally we need to write the test that actually returns the XMLDataProvider. So the final function that 'loadData' should call, after all those other function is, createXmlDataProvider. And you can override that to return an empty or dummy XmlDataProvider.
Notice that in your tests you have never gone to the real file system and really created an XMLDataProvider based on a file. But what you have done is to check every if statement in your loadData function. You've tested the loadData function.
Now you should write one more test. A test that uses the real file system and a real valid XML file.
When I look at the following code:
public class LocalizationData
{
private static bool IsXML(string fileName)
{
return (fileName != null && fileName.ToLower().EndsWith("xml"));
}
public XmlDataProvider LoadFile(string fileName)
{
if (!IsXML(fileName)) return null*;
return new XmlDataProvider{
IsAsynchronous = false,
Source = new Uri(fileName, UriKind.Absolute)
};
}
}
(* I'm not thrilled about the return null. Yuck! that smells.)
Anyway, I would ask the following questions to myself:
What could possibly break with this code? Are there any complex logic or fragile code that I should safe-guard myself against?
Is there anything complicated to understand or worth highlighting via a test that the code is not able to communicate?
Once I've written this code, how frequently do I think I'll revisit (change) it?
The IsXML function is extremely trivial. Probably does not even belong to this class.
The LoadFile function creates a synchronous XmlDataProvide if it gets a valid XML filename.
I would first search who uses LoadFile and from where fileName is being passed. If its external to our program, then we need some validation. If its internal and somewhere else we are already doing the validation, then we are good to go. As Martin suggested, I would recommend refactoring this to take Uri as the parameter instead of a string.
Once we address that, then all we need to know is if there is any special reason why the XMLDataProvider is in the synchronous mode.
Now, is there anything worth testing? XMLDataProvider is not a class we built, we expect it to work fine when we give a valid Uri.
So frankly, I would not waste my time writing test for this. In the future, if we see more logic creeping in, we might revisit this again.
In one of my (Python) projects, I assume that all unit tests are run in a special directory that contains the folders "data" (input files) and "output" (output files). I'm using a test script that first checks whether those folders exists (i.e. if the current working directory is correct) and then runs the tests. My unit tests can then use relative filenames like "data/test-input.txt".
I don't know how to do this in C#, but maybe you can test for existence of the file "data/azeri.xml" in the test SetUp method.
It has nothing to do with your testing (x), but consider using Uri instead of String as parameter type for your API.
http://msdn.microsoft.com/en-us/library/system.uri(v=VS.100).aspx
x: I think Steven covered that topic pretty very well.
Why do you use the XmlDataProvider? I don't think that it's a valuable unit test, as it stands now. Instead, why don't you test whatever you would do with that data provider?
For example, if you use the XML data to load out a list of Foo objects, make an interface:
public interface IFooLoader
{
IEnumerable<Foo> LoadFromFile(string fileName);
}
You can then test your implementation of this class using a test file you generate during a unit test. In this way you can break your dependency on the filesystem. Delete the file when your test exits (in a finally block).
And as for collaborators that use this type, you can pass in a mock version. You can either hand code the mock, or use a mocking framework such as Moq, Rhino, TypeMock or NMock. Mocking is great, but if you're new to TDD then it's fine to hand code your mocks while you learn what they're useful for. Once you have that, then you are in a good position to understand the good, bad and ugly of mocking frameworks. They can be a bit gnarly to work with when you're starting TDD. Your mileage may vary.
Best of luck.
In this case, you are basically at the lower level of dependency. You are testing that a file exist and that an xmlprovider can be created with the file as source.
The only way that you could break the dependency, would be to inject something to create the XmlDataProvider. You could then mock it to return a XmlDataProvider that you created (as opposed to read). As simplistic example would be:
class XmlDataProviderFactory
{
public virtual XmlDataProvider NewXmlDataProvider(string fileName)
{
return new XmlDataProvider
{
IsAsynchronous = false,
Source = new Uri(fileName, UriKind.Absolute)
};
}
class XmlDataProviderFactoryMock : XmlDataProviderFactory
{
public override XmlDataProvider NewXmlDataProvider(string fileName)
{
return new XmlDataProvider();
}
}
public class LocalizationData
{
...
public XmlDataProvider LoadFile(string fileName, XmlDataProviderFactory factory)
{
if (IsValidFileName(fileName))
{
return factory.NewXmlDataProvider(fileName);
}
return null;
}
}
[TestFixture]
class LocalizationDataTest
{
[Test]
public void LoadFile_DataLoaded_Succefully()
{
var data = new LocalizationData();
string fileName = "d:/azeri.xml";
XmlDataProvider result = data.LoadFile(fileName, new XmlDataProviderFactoryMock());
Assert.IsNotNull(result);
Assert.That(result.Document, Is.Not.Null);
}
}
Using an injection framework could simplify the call to LoadFile by injecting the factory in the class constructor or elsewhere.
I Like #Steven's answer except I think He didn't go far enough:
public interface DataProvider
{
bool IsValidProvider();
void DisableAsynchronousOperation();
}
public class XmlDataProvider : DataProvider
{
private string fName;
private bool asynchronousOperation = true;
public XmlDataProvider(string fileName)
{
fName = fileName;
}
public bool IsValidProvider()
{
return fName.ToLower().EndsWith("xml");
}
public void DisableAsynchronousOperation()
{
asynchronousOperation = false;
}
}
public class LocalizationData
{
private DataProvider dataProvider;
public LocalizationData(DataProvider provider)
{
dataProvider = provider;
}
public DataProvider Load()
{
if (provider.IsValidProvider())
{
provider.DisableAsynchronousOperation();
return provider;
}
return null;
}
}
By not going far enough I mean that he didn't follow the Last Possible Responsible Moment. Push as much down into the implemented DataProvider class as possible.
One thing I didn't do with this code, is drive it with unit tests and mocks. That is why you're still checking the state of the provider to see if it is valid.
Another thing is that I tried to remove the dependencies on having the LocalizationData know that the provider is using a file. What if it was a web service or database?
So first of all let us understand what we need to test. We need to verify that given a valid filename, your LoadFile(fn) method returns an XmlDataProvider, otherwise it returns null.
Why is the LoadFile() method difficult to test ? Because it creates a XmlDataProvider with a URI created from the filename. I have not worked much with C#, but am assuming that if the file does not actually exist on the system, we will get an Exception. The real problem is, your production method LoadFile() is creating something which is difficult to fake. Not being able to fake it is a problem because we cannot ensure the existence of a certain file in all test environments, without having to enforce implicit guidelines.
So the solution is - we should be able to fake the collaborators (XmlDataProvider) of the loadFile method. However, if a method creates it's collaborators it cannot fake them, hence a method should never create it's collaborators.
If a method does not create it's collaborators, how does it get them ? - In one of these two ways:
They should be injected into the method
They should be obtained from some factory
In this case it does not make sense for the XmlDataProvider to be injected into the method, since that is exactly what it is returning. So we should get it from a global Factory - XmlDataProviderFactory.
Here comes the interesting part. When your code is running in production, the factory should return an XmlDataProvider, and when your code is running in a test environment, the factory should return a fake object.
Now the only part of the puzzle is, how to ensure that the factory behaves in different ways in different environments ? One way is to use some properties which have different values in both environments, and the other way is to configure the factory for what it should return. I personally prefer the former way.
Hope this helps.
This time, don't try to break your dependency on the file system. This behavior clearly depends on the file system, and appears to be at the integration point with the file system, so test it with the file system.
Now, I second Bob's advice: throw this code away and try test-driving it. It makes for great practice and is exactly how I trained myself to do it. Good luck.
Instead of returning XmlDataProvider which ties you a specific tech, hide this implementation detail. It looks like you need a repository Role to
LocalizationData GetLocalizationData(params)
You can have an implementation for this Role, which internally uses Xml. You'd need to write integration tests to test whether XmlLocalizationDataRepository can read actual Xml data stores. (Slow).
The rest of your code can mock out GetLocalizationData()
we use the nunit.exe application to run our (integration)test
Now i experience the problem that the connectionstring is not picked up from the app.config from the dll where the testcode is in.
That sounds logical because the nunit.exe is the starting app and not the test dll (it used to work when i started the tests from the visual studio testframework by the way), but should i put the connectionstrings in the nunit.exe.config?
I tried setting them in the testcode (works for the appsettings : ConfigurationManager.AppSettings.Set("DownloadDirectory", mDir);) like this:
ConfigurationManager.ConnectionStrings.Add(conset); (where conset is a ConnectionStringSettings object), but then i get the error that the connectionstrings section is readonly.
What should i do to use the connectionstrings in my test?
EDIT:
we use the entity framework so we can't put the connectionstring in the appsettings because it reads from the section directly, i couldn't find a way to work around this behaviour.
Using reflection, you can (in memory) change your value of the Configuration.ConnectionStrings[connectionName], which in your case you would probably do in SetUp or perhaps TestFixtureSetUp. See http://david.gardiner.net.au/2008/09/programmatically-setting.html.
// Back up the existing connection string
ConnectionStringSettings connStringSettings = ConfigurationManager.ConnectionStrings[connectionName];
string oldConnectionString = connStringSettings.ConnectionString;
// Override the IsReadOnly method on the ConnectionStringsSection.
// This is something of a hack, but will work as long as Microsoft doesn't change the
// internals of the ConfigurationElement class.
FieldInfo fi = typeof(ConfigurationElement).GetField("_bReadOnly", BindingFlags.Instance | BindingFlags.NonPublic);
fi.SetValue(connStringSettings, false);
// Set the new connection string value
connStringSettings.ConnectionString = connectionStringNeededForNUnitTest;
I realize this is not the answer you are looking for, but it is the one I applied to solve your same problem:
You can modify, in EF5 and EF4.3 at least, your DbContext implementation and add a constructor that accepts a hard coded connection string, such as this:
public partial class MyContext : DbContext
{
public MyContext() : base("name=MyContext")
{
}
// --- Here is the new thing:
public MyContext(string entityConnectionString) : base(entityConnectionString)
{
}
// --- New thing ends here
// .... the rest of the dbcontext implementation follows below
}
You would have to paste this thing in every time you regenerate your context, but IMHO it's worth the hassle. The connection string has to be entity framework formatted with your metadata and everything, but you will be able to figure it out. Just keep it somewhere so you can paste it in whenever necessary.
You can read Connection String Value from ConfigurationManager.AppSettings, yes it is readonly. You can change it in App.Config.
If you want to change some values in connection string, for ex URL, in code you can change your dataContext.URL or any properties you want with coding.
I think for unit tests it may be much easy. you may put connection string into a test class directly as hardcoded string. in simple unit tests you test limited logic scope and not care of authentically of input arguments
I'm trying to dynamically create a connection string during compile time:
private static string m_ConnectionString
{
get
{
string connectionString = #"Data Source=" + myLibrary.common.GetExeDir() + #"\Database\db.sdf;";
return connectionString;
}
}
public static string ConnectionString = m_ConnectionString;
I keep running into type initialization errors. ConnectionString ends up null at runtime. I was trying to avoid having to set the connection string for all applications that use my code library. The location of the database is different for each project that uses the library. I have code that can determine the correction string, but was wanting to run it during class initialization. Is this even possible?
I agree with Oliver's approach to discover the error, but would like to add that you could put this in a static constructor. This would achieve your requirement of "during class initialization".
public static string ConnectionString { get; private set; }
static MyClass()
{
ConnectionString = #"Data Source=" + myLibrary.common.GetExeDir() + #"\Database\db.sdf;";
}
Just set a breakpoint and step into your function and try to find out what is going wrong.
Maybe there will be some exception be thrown which you actually don't see (in some underlying code). To find these cases you should go in Visual Studio to Debug - Exceptions and check all the boxes in the list. Maybe you can find this way, why you get a null instead of a string.
That code is executed at runtime, not compile time. I think you're going down the wrong track.
Another program running as a pre build event could modify the source code of the resources.resx file, prior to compilation. You then get your connection string as a resource string.
Kind of a hack, but not the worst thing I've ever seen. My versions numbers are incremented in a similar way.