I have two DLL files that have the same namespace but they have different methods and types.
How can I reference both DLLs in my project and use their methods and types?
By the way, these two DLLs have some methods and types with the same name but different implementation and some unique methods and types.
There's nothing special you need to do - just reference them and use the types. Namespaces can span accross several assemblies without problems, because they're not really opaque types. A namespace is just a way of adding a common prefix to all the types it contains, allowing you to have multiple types of the same name under different namespaces. (The framework doesn't see them as having the same names, because it sees the "fully qualified" name of everything - which has an alias and a namespace attached to the front of it.)
In the rare event that you reference 2 assemblies which have the same type names and the same namespaces (such as 2 different versions of the same dll) - you can distinguish which assembly to use for a given type using an alias. The default alias for all references is global, but you can specify your own alias for any assembly when you reference it (using a compiler switch - or just use the properties box in Visual Studio) - and have an extern alias <name> clause at the top of your code file where you use it - you would access the types from different assemblies with <name>::MyNamespace.Type
If you have 2 types with the exact same name (note that the name includes the namespace) but in different DLLs and you are interested in using both of them, then you can do this.
Short Answer
You have type Acme.Foo in 2 different DLLs and you want to use them. Give the reference an alias in the reference properties window (View | Properties Window) then use it like this:
extern alias TheAliasYouGaveTheReference
TheAliasYouGaveTheReference::Acme.Foo f = new
TheAliasYouGaveTheReference::Acme.Foo();
The default namespace is global for any C# program but note above we are using the alias we created instead of global.
The best approach is to NOT get into a situation like this in the first place, if both assemblies are your own, then do not create 2 types with the exact same name in the exact same namespace. But sometimes we do not control the source code so for those times, the above solution can be used.
Long Answer
I am copying most of the article from here so it is recorded here in case the article is no longer available.
How do you get into a situation like this?
Firstly, here is how you can replicate the scenario so it is really clear what we are talking about:
Create a C# Class Library called FooVersion1
Replace the template code in Class1.cs with the following:
using System;
namespace Acme
{
public class Foo
{
public void Bar()
{
Console.WriteLine("Bar");
}
}
}
Right-click on the solution in solution explorer and select Add | New Project
Save the current project (only applicable in express)
Select a Class Library in the new project dialog and change the project name to FooVersion2 and press OK
Replace the code in Class1.cs with the following:
using System;
namespace Acme
{
public class Foo
{
public void Bar()
{
Console.WriteLine("Bar");
}
public void Goo()
{
Console.WriteLine("Goo");
}
}
}
Usage of the type in Application
Ok so now we have 2 different assemblies containing Acme.Foo. Let's now create a console application and try to use each one.
Right-click on the solution in solution explorer and select Add | New Project
Select a Console Application and call it Consumer
Right-click on Consumer and select ‘Set as startup project’
Right-click on the references node in the Consumer project and select ‘Add Reference’
Click on the projects tab, and multi-select FooVersion1 and FooVersion2
Click OK
Add the following line to Main in the Program type of the Consumer project:
Acme.Foo f = new Acme.Foo();
Build the solution via Ctrl+Shift+B (or F6)
Notice that you get two build errors [as shown below]:
The Fix
Here is how we can fix it:
Open solution explorer and select FooVersion1 in the References folder of the Consumer project
Hit F4 (or select View | Properties Window)
Change the Aliases property to FooVersion1
Build the solution
Now everything will build correctly, because Acme.Foo unambiguously refers to FooVersion2
Add the following directive to the top of Program.cs in the Consumer project:
extern alias FooVersion1;
Change the usage of Acme.Foo to:
FooVersion1::Acme.Foo f = new FooVersion1::Acme.Foo();
f.Bar();
Notice that when you type ‘f.’ the completion list contains only those methods in FooVersion1 of Acme.Foo (notably it does not include Goo)
Build the solution and everything will build correctly
Finally add the following code under f.Bar() in Program.cs of the Consumer project:
Acme.Foo f2 = new Acme.Foo();
f2.Goo();
Notice that f2’s completion list contains Goo.
Build again using Ctrl+Shift+B and notice that there are still no build errors
you can use the alias feature of the /reference (Import Metadata) (C# Compiler Options) compiler option to solve your problems, read from here for more details
I want to fix my namespaces of a large solution containing several projects that got a bit messed up after copying and refactoring some UserControls...
My goal is simply that all namespaces match the folder structure a file is located in. There's always only one namespace per file.
How could I achieve this? I already know how to change a project's root namespace, but that's not what I need here.
Example:
The file ...\Project1\OneDirectory\Subdirectory\Code.cs contains the
namespace Project1.OtherDirectory.Subdirectory { /* ... */ }
This should get refactored to:
namespace Project1.OneDirectory.Subdirectory { /* ... */ }
Additional candy:
Reorganize using statements as well, so that unused namespaces are no longer included, but add those who changed and remove explicit namespace identifiers.
Example:
var c = new Project1.OneDirectory.Subdirectory.Code();
should become
using Project1.OneDirectory.Subdirectory;
/* ... */
var c = Code();
Given an instance of System.Reflection.Assembly.
I have come across this dilemma plenty of times when I want to load a resource from the current assembly by its manifest resource stream.
The fact is that if you embed a file as a resource in your assembly using Visual Studio its manifest resource name will be derived from the default namespace of the assembly as defined in the Visual Studio project.
The best solution I've come up with (to avoid hardcoding the default namespace as a string somewhere) is to simply ensure your resource loading code is ALWAYS happening from inside a class that's also in the default namespace and then the following near-generic approach may be used.
This example is loading an embedded schema.
XmlSchema mySchema;
string resourceName = "MyEmbeddedSchema.xsd";
string resourcesFolderName = "Serialisation";
string manifestResourceName = string.Format("{0}.{1}.{2}",
this.GetType().Namespace, resourcesFolderName, resourceName);
using (Stream schemaStream = currentAssembly.GetManifestResourceStream(manifestResourceName))
mySchema = XmlSchema.Read(schemaStream, errorHandler);
See also: How to get Namespace of an Assembly?
Edit: Also noticed a very detailed answer to the question I'm answering at http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/3a469f5d-8f55-4b25-ac25-4778f260bb7e
Another edit in case people with same question come looking: Excellent idea to solve the resource-loading question here: How get the default namespace of project csproj (VS 2008)
Not possible. Nothing specifies a "Root" namespace. The default namespace in the options is a visual studio thing, not a .net thing
There could be any number of namespaces in a given assembly, and nothing requires them to all start from a common root. The best you could do would be to reflect over all the types in an assembly and build up a list of unique namespaces contained therein.
I just created an empty internal class called Root and put it in the project root (assuming this is your root namespace). Then I use this everywhere I need the root namespace:
typeof(Root).Namespace;
Sure I end up with an unused file, but it's clean.
Assemblies don't necessarily have a root namespace. Namespaces and Assemblies are orthogonal.
What you may be looking for instead, is to find a type within that Assembly, and then find out what its namespace is.
You should be able to accomplish this by using the GetExportedTypes() member and then using the Namespace property from one of the returned Type handles.
Again though, no guarantees all the types are in the same namespace (or even in the same namespace hierarchy).
I use typeof(App).Namespace in my WPF application.
App class is mandatory for any WPF application and it's located in root.
Get Types gives you a list of Type objects defined in the assembly. That object has a namespace property. Remember that an assembly can have multiple namespaces.
GetType(frm).Namespace
frm is the startup Form
Namespaces have nothing to do with assemblies - any mapping between a namespace and the classes in an assembly is purely due to a naming convention (or coincidence).
There actually is an indirect way to get it, by enumerating the names of the assembly's manifest resources. The name you want ends with the part of it that you know.
Rather than repeat the code here, please see get Default namespace name for Assembly.GetManifestResourceStream() method
The question I had that landed me here was, "If I call library code N methods deep and want the namespace of the Project - for example the MVC app that's actually running - how do I get that?"
A little hacky but you can just grab a stacktrace and filter:
public static string GetRootNamespace()
{
StackTrace stackTrace = new StackTrace();
StackFrame[] stackFrames = stackTrace.GetFrames();
string ns = null;
foreach(var frame in stackFrames)
{
string _ns = frame.GetMethod().DeclaringType.Namespace;
int indexPeriod = _ns.IndexOf('.');
string rootNs = _ns;
if (indexPeriod > 0)
rootNs = _ns.Substring(0, indexPeriod);
if (rootNs == "System")
break;
ns = _ns;
}
return ns;
}
All this is doing is getting the stacktrace, running down the methods from most recently called to root, and filtering for System. Once it finds a System call it knows it's gone too far, and returns you the namespace immediately above it. Whether you're running a Unit Test, an MVC App, or a Service, the System container is going to be sitting 1 level deeper than the root namespace of your Project, so voila.
In some scenarios where System code is an intermediary (like System.Task) along the trace this is going to return the wrong answer. My goal was to take for example some startup code and let it easily find a class or Controller or whatever in the root Namespace, even if the code doing the work sits out in a library. This accomplishes that task.
I'm sure that can be improved - I'm sure this hacky way of doing things can be improved in many ways, and improvements are welcome.
Adding to all the other answers here, hopefully without repeating information, here is how I solved this using Linq. My situation is similar to Lisa's answer.
My solution comes with the following caveats:
You're using Visual Studio and have a Root Namespace defined for your project, which I assume is what you're asking for since you use the term "root namespace"
You're not embedding interop types from referenced assemblies
Dim baseNamespace = String.Join("."c,
Me.GetType().Assembly.ManifestModule.GetTypes().
Select(Function(type As Type)
Return type.Namespace.Split("."c)
End Function
).
Aggregate(Function(seed As String(), splitNamespace As String())
Return seed.Intersect(splitNamespace).ToArray()
End Function
)
)
Here as a rather simple way to get the root namespace for a website project.
''' <summary>
''' Returns the namespace of the currently running website
''' </summary>
Public Function GetWebsiteRootNamespace() As String
For Each Asm In AppDomain.CurrentDomain.GetAssemblies()
If Asm Is Nothing OrElse Asm.IsDynamic Then Continue For
For Each Typ In Asm.GetTypes
If Typ Is Nothing OrElse Typ.Name Is Nothing Then Continue For
If Typ.Name = "MyProject" Then Return Typ.Namespace.Split("."c)(0)
Next
Next
Return Nothing
End Function
This simply checks all the loaded assemblies for the "MyProject" type and returns the root namespace for that type. This is useful for logging when you have multiple web projects in a single solution sharing a log system. Hope this helps someone.
This solution works if you are trying to load an embedded resource.
var assembly = System.Reflection.Assembly.GetExecutingAssembly();
string[] resourceNames = assembly.GetManifestResourceNames();
string resourceNameNoNamespace = $"Languages.{languageSupport.IsoCode}.Languages.xml";
var match = resourceNames.SingleOrDefault(rn => rn.EndsWith(resourceNameNoNamespace));
Dim applicationNamespace = TextBeforeFirst(Assembly.GetCallingAssembly().EntryPoint.DeclaringType.Namespace, ".")
Public Function TextBeforeFirst(value As String, expression As String) As String
If String.IsNullOrEmpty(value) Or String.IsNullOrEmpty(expression) Then Return Nothing
Dim index = value.IndexOf(expression)
If index = -1 Then Return Nothing
Dim length = index
Return value.Substring(0, length)
End Function
I have a class let's say it's called "Apples". Let's say that class is in a .cs file in a folder called "Apples"
Project
-Apples
-Apples.cs
-main.cs
How can i reference it without writing this:
Main.cs
Apples.Apples.testVar = 2;
and just write
Main.cs:
Apples.testVar = 2;
Is there a way to do this, or will i have to put up with it or change the folder name?
put this at the top of your file -
using Apples = Apples.Apples;
If you have a folder in visual studio and create a class in it, Visual Studio (and possibly other IDEs) will automatically append the folder's name to the namespace of any file created from that folder.
That DOES NOT mean in any way that the namespace has to stay that way. The "folder" is purely for organizational purposes and plays no part in the compilation of your code. The filename doesn't matter to the actual code either. If you look in your Apples.cs just change:
namespace Apples.Apples
{
//....
to
namespace Apples
{
//...
It's simply the rule that your IDE is using as an assumption to what you want. You're not required to follow it.
EDIT: At least that's what I assume to be the misunderstanding here as you're focusing on the folder name - which means nothing to the code and only matters to you. Additionally as previously mentioned you might be hung up on ambiguity between namespace name and class name. As mentioned in other answers it's a bad idea to name a class the same as it's namespace.
By default the global namespace for your project will be the same name as your project. So if you named your project "Apples" and then made a folder called "Apples" and created a class within that folder called "Apples" - You'd then navigate to your class by following the chain of namespaces:
Apples.Apples.Apples
You're drawing the conclusion that you have to do this based on the folder/file names but it's really the namespaces/classes. You have several options here but the bottom line is in order to remove confusion and mess 2 or all 3 of those "Apples" need to change. Changing the file name or folder name will not work. you have to change the class name and at least one of the namespace names. Something more appropriate:
AppleProject.Apples.AppleBase
or even as simple as:
Apples.Apple // removed the extra namespace in the middle
You could alias "Apples" in your using statements:
using Apples = Apples.Apples.testVar;
Or whatever you'd like to make it easier to read.
Yes if you are using C# you just add it in the using references up top of your code file you are on:
EG:
using Apples.Apples;
You just need to ensure you have the reference to the project set if it is not in your current project.
I have an ASP.net MVC 3 project with resource files setup in folders like:
/Resources/EntityName/Views/
/Resources/EntityName/Models/
This means the namespace to access the strongly typed resource values is:
Resources.EntityName.Models.ModelA.Property1
Visual studio gives a compile time error if I try to include the namespace "resources.xxx" and it won't allow the using alias syntax either.
Is there anyway to include or atleast alias the strongly typed namespace of a resource file like it was a normal namespace?
There should be no reason why you can't use one of these objects within a class:
using YourProject.Resources.EntityName.Models;
You might try something like this (not tested, just an idea)
public class myModelA : Resources.EntityName.Models.ModelA
{ /*Leave empty here, nothing to do*/ }
Then you may be able to call the shortest myModelA instead of the complete, verbose name of the resource. Watch out because you'll not be able to access private members of your original model if you inherit it like thi.