there is no place for assemlbies in my project. I tried many methods to find it, but without success.
The problem is that it can't find the class - it's not in the same namespace as your current code.
That may be it's in a different project in the current solution, in a external DLL, or just in a different namespace in another file in the current project.
Start by hovering the mouse over the error, and open the drop down that appears. If it has an "include" option, click that, and it should fix it.
If it doesn't, you need to find out where that class is, and add a reference to uit, either via the project in the same solution, or via the DLL, and then add the appropriate using line to the top of all files that reference it.
I am creating a Class Library and need to inherit from PictureBox: public class Picture : PictureBox { ... } but Forms is not available when I try to add a using directive for it at the top of my Class Library: using System.Windows.Forms;. I know that I can get it to work by right-clicking Referenced in Solution Explorer and selecting Add Reference, then adding the System.Windows.Forms assembly from the list.
But is it okay to do this? Is it okay to reference WindowsForms from a Class Library?
It is totally okay to do this.
System.Windows.Forms is just an assembly like any others. There is no special treatment to the project file, as with for example Office add-ins.
You can safely add this assembly to your project file.
I'm attempting to inherit from the WeakEventManager class but the namespace can't be found in my project. I'm not sure what's going on as I have the using System.Windows; directive. I can load a project that uses this class successfully I just can't seem to implement it on my own. The project is .Net 4.5 and I'm unsure as to what's happening.
Any help is appreciated. Thanks in advanced.
The class lives in the System.Windows namespace, but is defined in the WindowsBase assembly. Make sure you have imported the WindowsBase assembly and added it as a reference to your project.
In Solution Explorer
open your project
right-click on References
click Add Reference
select .NET tab
select System.Windows
click OK
In Solution Explorer
open your project
right-click on References
click Add Reference
select .NET tab
select WindowsBase
I have been trying to include DirectX in C sharp project (Visual Studio 2010).
I installed DirectX SDK and included the components as:
using Microsoft.DirectX;
using Microsoft.DirextX.Direct3D;
When I try to compile, I get the error: the type or namespace name 'directx' does not exist in the namespace 'microsoft'
Some blogs mentioned that I need to add 'reference' - Microsoft.DirectX under '.NET' tab. But I couldn't find it over there. Neither was any facility to add it to the tab.
Any suggestion will be highly appreciated.
This was deprecated a long time ago. The last Direct SDK that still has the managed wrappers is February 2010. The download is available here. You'll get to pick the references you are looking for after you install that one.
Better not to use it, no future, look at something like the open source SlimDX or SharpDX projects.
There are various reasons why a dll would not appear on the .Net tab.There is specific registry configuration that makes certain dlls to appear on the .Net tab.
Alternatively use the browse option to add the dll reference manually to your project.
Project >> Add Reference
This is the way to add reference for Directx in C# Program :
Go to the solution explorer
Click references
Click add reference
Click Browse
Go to : "C:\WINDOWS\Microsoft.NET\DirectX for Managed Code\1.0.2902.0\"
*usually this is the place of Directx Files located. This can be change with the installation of .net.
Select your DirectX package.
example :
(C:\Windows\Microsoft.NET\DirectX for Managed Code\1.0.2902.0\Microsoft.DirectX.dll)
Here is one way i have find. First you need to install DXSDK (i have June2010 and SDK for Windows 7). Go to "Add refference" dialog press "Browse" , go to something like this "C:\Windows\Microsoft.NET\DirectX for Managed Code\1.0.2902.0" or "C:\Windows\Microsoft.NET\Managed DirectX\v9.02.2904" then choose proper dll for example - Microsoft.DirectX.dll. So you can add "using Microsoft.DirectX" directive to your project.
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.