I'm new to c# and visual studio..
currently i'm developing a metro application fro windows 8 that works as a proxy switcher application..
when I using this code
System.Net.GlobalProxySelection.Select = new System.Net.WebProxy(proxyURI);
it says GlobalProxySelection does not exist in the System.Net.... I imported system.net at the begining of the code..
Edit
no problem with System.net... no errors showing at there.. But the thing is I cant use "GlobalProxySelection" and "WebProxy" classes..
Also Target framework is locked in application properties..
It is likely you haven't added a reference to the System.Net assembly. See this article from MSDN which should give you more info on adding this reference.
The System.Net namespace is in the system.dll assembly. I would be surprised if that weren't already referenced when you started the project, but to be safe, you should ensure that a reference to this dll exists. If it doesn't, then add it.
You can always find this kind of information on MSDN: GlobalProxySelection Class. In the Inheritance Hierarchy section, there is namespace/assembly info.
The only other thing I can think of is maybe you've added a reference to some other assembly that has this namespace (seems unlikely, but possible).
If you go to your project's properties, what is your target framework? It might be that is's accidentally using the "Client Profile" version of the framework, which misses quite a few bits and pieces. If so, change it to the normal version and then it might suddenly exist.
You can change your Target Framework on Application section and don't fix to Client Profile
Related
I'm trying to use DataAnnotations in my WPF project to specify a maximum length of strings, with the following:
using System.ComponentModel.DataAnnotations;
However, I get the error
The type or namespace name 'DataAnnotations' does not exist in the
namespace 'System.ComponentModel' (are you missing an assembly
reference?)
I've seen other examples where DataAnnotations does exist in this namespace. I'm using C#4. Is there any reason why I can't use this? What can I do to fix it?
You have to reference the assembly in which this namespace is defined (it is not referenced by default in the visual studio templates). Open your reference manager and add a reference to the System.ComponentModel.DataAnnotations assembly (Solution explorer -> Add reference -> Select .Net tab -> select System.ComponentModel.DataAnnotations from the list)
If using .NET Core or .NET Standard
use:
Manage NuGet Packages..
instead of:
Add Reference...
To Reference System.ComponentModel.DataAnnotations
In a code file to have Using System.ComponentModel.DataAnnotations; at the top of the file such as:
using System.ComponentModel.DataAnnotations;
Add a .NET reference to your project by right clicking the project in solution explorer:
Hope this helps! This question helped me.
If you don't have it in references (like I did not) you can also add the NuGet System.ComponentModel.Annotations to get the assemblies and resolve the errors. (Adding it here as this answer still top of Google for the error)
I also had the same problem and I resolved by adding the reference in one of my projects which didn't had the mentioned reference. If you have 2-3 projects in your solution, then check by adding this reference to the other projects.
I found that I cannot reference System.ComponentModel.DataAnnotations from Silverlight 5 with the below version at (1). I found that Silverlight 5 assemblies cannot use .NET assemblies, it gives the error "You can't add a reference to System.ComponentModel.DataAnnotations as it was not built against the Silverlight runtime. ..." I plan to workaround this by hopefully installing the Silverlight 5 package found at (2) below. If this fails I will update this post.
[UPDATE: it failed. I installed everything relating to Silverlight 5 and I don't have the Silverlight version of the .dll assembly System.ComponentModel.DataAnnotations . Too bad. UPDATE II: I found an old .dll having this name from a previous installation of Silverlight developer's kit for Visual Studio 2008 or 2010. I added this file and it seems to 'work', in that IntelliSense is now recognizing attributes on class members, such as [Display(Name = "My Property Name")]. Whether or not this works for everything else in this .dll I don't know.]
(1)
Microsoft Visual Studio Professional 2013
Version 12.0.21005.1 REL
Microsoft .NET Framework
Version 4.5.51641
Installed Version: Professional
(2)
http://go.microsoft.com/fwlink/?LinkId=229318
I searched for help on this topic as I came across the same issue.
Although the following may not be the Answer to the question asked originally in 2012 it may be a solution for those who come across this thread.
A way to solve this is to check where your project is within the solution. It turns out for my instance (I was trying to install a NuGet package but it wouldn't and the listed error came up) that my project file was not included within the solution directory although showing in the solution explorer. I deleted the project from the directory out of scope and re-added the project but this time within the correct location.
Use the FrameWork version 4.5 and above for your project then problem solved.Because this namespace is under 4.5 and above.
System.ComponentModel.DataAnnotations is contained in its own assembly so you need to make sure you have it refernced. Just simply:
1). Right click on Soloution and choose add.
2). Choose reference from the list.
3). Search " System.ComponentModel.DataAnnotation " and tick the check box on its left hand side and press ok.
Job done, shouldnt have any refernce errors.
If you tried to update visual studio from vs2008 to vs2010. And your app uses framework 3.5 (and you don't want to upgrade it), and also used WCF RIA Services BETA... I have bad news... you MUST upgrade to WCF RIA Services v1 (BETA does not work on vs2010)... and due to this... you also have to install Silverlight 4 + upgrade to framework 4.0
See this:
http://blog.nappisite.com/2010/05/updating-visual-studio-2008net-35-ria.html
I upgraded from Silverlight 4 to Silverlight 5 and then I was having this issue. Although I had a reference to "System.ComponentModel.DataAnnotations" under "References" in my project, it had a yellow yield sign by it that indicated the previously referenced assembly could not be found. It turned out that the properties of the "System.ComponentModel.DataAnnotations" reference indicated "Specific Version = True", when I changed this to "Specific Version = False" it fixed the issue. Right click on the "System.ComponentModel.DataAnnotations" assembly under "References" and select "Properties" from the context menu. Check that the property value for "Specific Version = False".
It must have been referencing the old Silverlight 4 assembly which was no longer available after the upgrade to Silverlight 5.
I also have this problem.
That is very stupid when i add a namespace the same with System. I try to remove all references, but it is not resolved. I use "global::System.ComponentModel", it is working as well.
When i remove my namespace, this problem has been resolved.
For .Net Core in Visual Studio 2019 try this.
see VS suggestion
It worked for me, hope it'll work for you as well.
I was moving from .Net Framework 4.7.2 to .Net Standard 2.0.
In my case, I had to change DataAnnotations's reference from an Assembly reference to a Nuget package.
This error occurs when the reference to the "System.dll" got removed.Solution to the problem is very simple add the reference to "System.dll".The dll is normally available in the following location
"C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727" .Add the reference your problem will get solved .
There was a problem using System.ComponentModel.DataAnnotation in net40 so I just did:
#if !NET40
using System.ComponentModel.DataAnnotations;
#endif
#if !NET40
[StringLength(256)]
#endif
The NET40 must be a predefined macro definition for .Net Framework 4.0
I had same problem, I solved this problem by following way.
Right click on page, select Property. in build action select Content.
Hope that this solution may help you.
this is my problem with VS :S
in the first project :
System.Security.Cryptography.AesCryptoServiceProvider obj;
everything is ok
in the second project:
System.Security.Cryptography.AesCryptoServiceProvider obj1;
it doesn't recognize the AesCryptoServiceProvider?!!
is VS using different packages or what ?!
updated: changed the variable name but still not working
var is a reserved keyword. Use a different identifier name or #var.
System.Security.Cryptography.AesCryptoServiceProvider #var;
This may not be the problem - you need to ensure that each project has a reference to System.Core the assembly containing System.Security.Cryptography.
You will also need to ensure that you are targeting a framework version that contains this class (.NET 3.5 and above) - this can be done in the project property pages.
Check if both projects are referencing System.Core. Probably only the first one has it. You've to add it on both to be able to use AesCryptoServiceProvider.
Moreover, as you can see here AesCryptoServiceProvider is only available since .NET 3.5. Check your project's properties, in particular the Target Framework.
Are the references the same between both project? Just open references and see. I bet you are missing one. However, you really should use a different variable name than var. Also, can you post the exact error?
You can't name a variable var because it's a reserved word, use a different name, this will not cause an error :
System.Security.Cryptography.AesCryptoServiceProvider _var;
Edit :
AesCryptoServiceProvider is only supported in .Net framework 4 and 3.5 SP1, change the target framework and it will work and be sure to have System.Security.Cryptography; in that file.
I'm stuck with a project that I can't get "seen" in a reference by other projects in the same solution.
This is the error: Error 2 Metadata file 'C:\Documents and Settings\user\Desktop...\bin\Debug.dll' could not be found.
I've added the reference of course, and added the using directive for the namespace where it's used in class files. I remove the file, save, restart, and start anew, and it persists. Any ideas? I've been searching for hours, and it seems as though this can be caused by many things, none of which pertain to me. :/
It's a simple set of three class libraries and one windows forms project in the solution, VS 2010 Express, C#.
Within the same solution, but not within the same project? Are you sure you've declared your classes as public? They're internal by default.
Is one of your projects using .net 4 Client Framework and the referenced one isn't?
Have you added a project reference or a DLL reference between the projects? IS the name of the assembly you are referencing, really Debug.dll?
This is a little old, but thanks to the advice here I found my problem.
One project was using ".NET Framework 4 Client Profile" and the other ".NET Framework 4". I switched them both to use ".NET Framework 4" and it works fine now.
This question already has answers here:
Getting "type or namespace name could not be found" but everything seems ok?
(44 answers)
Closed 8 years ago.
I have a C# solution with several projects in Visual Studio 2010.
One is a test project (I'll call it "PrjTest"), the other is a Windows Forms Application project (I'll call it "PrjForm"). There is also a third project referenced by PrjForm, which it is able to reference and use successfully.
PrjForm references PrjTest, and PrjForm has a class with a using statement:
using PrjTest;
Reference has been correctly added
using statement is correctly in place
Spelling is correct
PrjTest builds successfully
PrjForm almost builds, but breaks on the using PrjTest; line with the error:
The type or namespace name 'PrjTest' could not be found (are you missing a using directive or an assembly reference?)
I've tried the following to resolve this:
Removed Resharper (since Resharper had no trouble recognizing the referenced project, I thought it might be worth a shot)
Removed and re-added the reference and using statement
Recreated PrjForm from scratch
PrjForm currently resides inside the PrjTest folder, I tried moving it to an outside folder
Loaded the solution on a different computer with a fresh copy of VS 2010
I have done my homework and spent far too long looking for an answer online, none of the solutions has helped yet.
What else could I try?
See this question.
Turns out this was a client profiling issue.
PrjForm was set to ".Net Framework 4 Client Profile"
I changed it to ".Net Framework 4", and now I have a successful build.
Thanks everyone!
I guess it figures that after all that time spent searching online, I find the solution minutes after posting, I guess the trick is knowing the right question to ask..
In my case I had:
Referenced DLL : .NET 4.5
Project : .NET 4.0
Because of the above mismatch, the 4.0 project couldn't see inside the namespace of the 4.5 .DLL. I recompiled the .DLL to target .NET 4.0 and I was fine.
PrjForm was set to ".Net Framework 4 Client Profile" I changed it to ".Net Framework 4", and now I have a successful build.
This worked for me too. Thanks a lot. I was trying an RDF example for dotNet where in I downloaded kit from dotnetrdf.
NET4 Client Profile:
Always target NET4 Client Profile for all your client desktop applications (including Windows Forms and WPF apps).
NET4 Full framework:
Target NET4 Full only if the features or assemblies that your app need are not included in the Client Profile. This includes:
If you are building Server apps, Such as:
ASP.Net apps
Server-side ASMX based web services
If you use legacy client scenarios, Such as:
o Use System.Data.OracleClient.dll which is deprecated in NET4 and not included in the Client Profile.
Use legacy Windows Workflow
Foundation 3.0 or 3.5 (WF3.0 , WF3.5)
If you targeting developer scenarios and need tool such as MSBuild or need access to design assemblies such as System.Design.dll
Another thing that can cause this error is having NuGet packages that have been built with a newer version of .NET.
The original error:
frmTestPlanSelector.cs(11,7): error CS0246: The type or namespace name 'DatabaseManager'
could not be found (are you missing a using directive or an assembly reference?)
Further up in the log I found this:
C:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets(1605,5): warning MSB3275: The primary reference "[redacted]\DatabaseManager\bin\Release\DatabaseManager.dll" could not be resolved because it has an indirect dependency on the assembly "System.Data.SQLite, Version=1.0.94.0, Culture=neutral, PublicKeyToken=db937bc2d44ff139" which was built against the ".NETFramework,Version=v4.5" framework. This is a higher version than the currently targeted framework ".NETFramework,Version=v4.0".
The solution was to re-install the NuGet packages:
http://docs.nuget.org/docs/workflows/reinstalling-packages
I solved mine because the other project was coded with .NET 4.5 and the other one was coded 4.0
The using statement refers to a namespace, not a project.
Make sure that you have the appropriately named namespace in your referenced project:
namespace PrjTest
{
public class Foo
{
// etc...
}
}
Read more about namespaces on MSDN:
Using Namespaces
I encountered this issue it turned out to be.
Project B references Project A.
Project A compiled as A.dll (assembly name = A).
Project B compiled as A.dll (assembly name A).
Visual Studio 2010 wasn't catching this. Resharper was okay, but wouldn't compile. WinForms designer gave misleading error message saying likely resulting from incompatbile platform targets.
The solution, after a painful day, was to make sure assemblies don't have same name.
It is also possible, that the referenced projects targets .NET 4.0, while the Console App Project targets .NET 4.0 Client Library.
While it might not have been related to this particular case, I think someone else can find this information useful.
The compiled dll should have public Class.
I had the same issue. The target frameworks were fine for me. Still it was not working.
I installed VS2010 sp1, and did a "Rebuild" on the PrjTest. Then it started working for me.
Other problem that might be causing such behavior are build configurations.
I had two projects with configurations set to be built to specific folders.
Like Debug and Any CPU and in second it was Debug and x86.
What I did I went to Solution->Context menu->Properties->Configuration properties->Configuration and I set all my projects to use same configurations Debug and x86 and also checked Build tick mark.
Then projects started to build correctly and were able to see namespaces.
Changing the framework to
.NET Framework 4 Client Profile
did the job for me.
For COM/ActiveX references, VS 2012 will show this error right on using statement. Which is quite funny, since it's saying that may be you are missing a using statement.
To solve this: register the actual COM/ActiveX dll even if it's in the neighbor project, and add a reference through COM channel, not project channel. It will add Interop.ProjectName instead of ProjectName as a reference and this solves this strange bug.
If your project (PrjTest) does not expose any public types within the PrjTest namespace, it will cause that error.
Does the project (PrjTest) include any classes or types in the "PrjTest" namespace which are public?
just changed Application's target framework to ".Net Framework 4".
And error got Disappeared.
good luck;
:D
check your Project Properties, your Reference Paths should be empty like this:
Regards
I used code from here and I get the following error:
Can't use HttpContext.Current.Server.MapPath()
In Visual Studio 2008 does the ContextMenuEntry "Solve" help you when you have missing references?
I already found out that HttpContext is not a member of System.Web in my IDE.
According to Help > Info I am using .NET 3.5 SP1.
How do I get that running?
How do u usually react in this situation? What stuff do u look for in msdn.com?
What I would do in that situation is look on MSDN (or Google) for HttpContext. I did that, and it says it’s in System.Web. So make sure your project has a reference to System.Web.
... and then it seems to work:
You can look in the documentation for the HttpContext class, and it tells you that it's in the System.Web namespace, in the System.Web.dll library.
So, to use it you need a reference to the System.Web.dll library, and you either need a using System.Web; statement, or use the fullly qualified name System.Web.HttpContext.Current.Server.MapPath.
However, are you sure that you want to use the MapPath method? The method gets the physical path of a web reference to a file. If the path to your CSV file is a web reference, for example "/data/items.csv" then you want to use the MapPath method, but if you have a physical path like for example "C:\mydata\items.csv" then you don't want to convert it.
Also, the MapPath only works if you actually are in a web application, where there is a HTTP context.
Timwi has it right, but for completeness. No, VS does not have the 'Solve' capability built in, however this functionality has been partially added by some add-ons. For example, Resharper will add the option to add the reference and using when needed -- but it does have to have been referenced before in the solution so it doesn't solve the initial find problem.
It was a simple case of not using the right framework, by that I mean the full fat version rather than the default 'light' version.
Right click on the Project and then Properties and make sure the full version of the latest framework is selected ie '.NET Framework 4', not '.NET Framework 4 Client Profile'
Try to add a reference to System.Web in your project.
HttpContext is a member of System.Web.
http://msdn.microsoft.com/en-us/library/system.web.httpcontext.aspx