Develop Reference

Problem with reference to another project

I have 1 solution with 2 projects (TcpClient and TcpServer) in TcpProtocol namespace.
Folders:
TestProject/source/TcpProtocol.Client/TcpClient.cs
TestProject/source/TcpProtocol.Server/TcpServer.cs
I have added this to the TcpClient project:
using static TcpProtocol.Server; // for use static values in TcpProtocol.Client.
But when I try to build a project, I get the following error message:
"The type or namespace 'Server' does not exist in the namespace 'TcpProtocol' (are you missing an assembl reference?)"
It's strange, because reference exist, but under name of reference I see yellow triangle.
If instead of using static write like this in code all work fine:
TcpProtocol.Server.port = 8008;
Why doesn't it work with static? How do I fix it?

Never used that before but I would understand the docs that you have to target a type/class.
Your code sample seems to target a namespace...

"The name does not exist in the namespace error" in XAML

I know this is a recurring error but I can't seem to get around it.
Intellisense does recognize the name of my custom control and suggests to add the proper using: directives, but not only XAML designer doesn't find the name of the control but I can't get through compilation either.
The custom control is a public class defined as
namespace MyApp.CustomControls
{
public class CustomTextBox : TexBox
{
...
}
}
And in my MainPage.xaml
<Page ...
xmlns:customControls="using:MyApp.CustomControls">
...
<customControls:CustomTextBox/>
...
</Page>
This does not render in design nor compile.
This answer and the ones below are not working for me.
The error message:
Error XDG0008 The name "CustomTextBox" does not exist in the namespace "using:MyApp.CustomControls".

Your code should works well after you build the project, and it works well in my side using your above code. Try to clean your solution or delete the bin and obj folders in your project then rebuild your app again. Also try to restart your Visual Studio. If it still happens, you can provide a reproducible sample to help me look into this issue.

I've seen quite a lot solutions saying that you should rebuild the project, restart Visual Studio or restart the machine.
What worked for me was specifying the assembly in the namespace reference, that is:
xmlns:the_namespace="clr-namespace:the_namespace" - produces the above error.
xmlns:the_namespace="clr-namespace:the_namespace;assembly=the_assembly" - works well.

I got a version of this error in my embedded UserControl when I tried to use the Name property in my XAML instead of using x:Name. In other words, when my XAML code looked like this:
myUserControls="using:MyUserControls"
<myUserControls:GraphCanvas Name="GraphCanvas" />
I got an error that 'The name "GraphCanvas" does not exist in the namespace "using:MyUserControls"'. When I changed one line of code to this:
<myUserControls:GraphCanvas x:Name="GraphCanvas" />
Everything built just fine.
I'm dropping this solution here because it took me about a day and a half to figure out this problem and this was the only stackoverflow page I found when I searched the error string. Hopefully I will save someone else the hassle I went through.

Namespace not recognised in using statement. "The type or namespace '#' does not exist in the namespace '#'. Are you missing an assembly reference?

I have a solution with about 14 projects, and am having a problem with a link I am trying to make between two of the projects:
Argus.Web (a web application project)
Argus.Domain.Office.Command (a project that reads data from an API and stores data in a local SQL Server database)
(there is also a project called Argus.Domain which I mention as it may possibly be part of the problem, although it hasn't caused problems in other similar places in my code.)
Argus.Domain.Office.Command has a context (argusOfficeContext) linking it to a database which I would like to access from Argus.Web. (This context works well in other situations.) When I try to add a using directive to reference the context's namespace in a class within Argus.Web I get the error in the title.
Here is the class I am scaffolding up (in Argus.Web) where the error occurs:
using Argus.Domain.Office.Command.Models;
namespace Argus.Web
{
public partial class Calculator
{
}
}
The red wiggly line appears only under 'Office' in the using, and the error in full is "The type or namespace 'Office' does not exist in the namespace 'Argus.Domain'. Are you missing an assembly reference?".
I have checked that the project Argus.Domain.Office.Command is referenced from Argus.Web and when I check Argus.Web build dependencies I see Argus.Domain.Office.Command (as well as the other project Argus.Domain), and it is set to build before Argus.Web. When I check in Argus.Web References > Projects the project Argus.Domain.Office.Command has a tick next to it and I conclude that it is therefore referenced.
Following Peter D's comment I checked the namespace declaration, and it is declared in the project Argus.Domain.Office.Command.
(Probably irrelevant:) here is the class I am trying to reference
using System.Data.Entity;
using Argus.Domain.Office.Command.Models.Mapping;
namespace Argus.Domain.Office.Command.Models
{
public partial class argusOfficeContext : DbContext
{
static argusOfficeContext()
{
Database.SetInitializer<argusOfficeContext>(null);
}
public argusOfficeContext()
: base("Name=argusOfficeContext")
{
}
public DbSet<Location> Locations { get; set; }
public DbSet<LocationPeriodReport> LocationPeriodReports { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Configurations.Add(new LocationMap());
modelBuilder.Configurations.Add(new LocationPeriodReportMap());
}
}
}
Both projects target .NET Framework 4.5.1, and I have looked for the answer in various places, but the fixes for the other questions below don't seem to fix my case. I'm running Visual Studio 2015. Other questions for reference:
'Using' not detecting namespace-checked client profiling already
Visual Studio 2010 suddenly can't see namespace?
Visual Studio 2015 C# Not finding references
If anyone can advise what I'm doing wrong I would really appreciate it. I have checked lots of other posts looking for an answer, but if you can provide a link to an answer I have missed that would also be great.

Most of the times I see this, the cause is a class with the same name as part of the namespace. These are in two different assemblies.
namespace Library.Foo // assembly 1
{
using Library.Foo.Bar; // error here
public class Bar
{
public void DoIt()
{
new Bell(); // and here
}
}
}
namespace Library.Foo.Bar // assembly 2
{
public class Bell
{
}
}
This can be a real pita to find. I suggest doing a test search of each word in your namespace. You're looking for a class of the same name.
As a side (and there's controversy over this), you can avoid some of these collisions by moving the using inside the namesapce.

OK, so I came up with a solution.
I thought I would try removing and recreating the references, and in a nutshell, this worked. Detail:
I right clicked on Argus.Web in the solution explorer, and then Build Dependencies > Project Dependencies. I tried deselecting Argus.Domain.Office.Command, but got the error 'This dependency was added by the project system and cannot be removed'. I'm not sure why this error appears, but I therefore tried right clicking on the references in Argus.Web, and selected 'Add Reference'. In the Projects section of the window that came up I was able to deselect Argus.Domain.Office.Command, so I did this, commented out the problematic using directive, cleaned and rebuilt my solution, added the reference back (right clicking on the references in Argus.Web, and selecting 'Add Reference'), and it all works again.
I guess that the original references must have been misconfigured, but at present I can't see how this came about. I will add to this post if I work out how this happened.
Many thanks to all respondees, all comments and answers were useful.

Why can Visual Studio detect which "using" is needed, but then say the type or class which provoked the addition of the reference does not exist?

On trying to build, all of a sudden (a couple of days since I worked on this project) I get:
"The type or namespace name 'IO' does not exist in the class or namespace 'OpenNETCF' (are you missing an assembly reference?)"
But when I comment out that line (using OpenNETCF.IO.Ports;), I get:
? OpenNETCF.IO.Ports.Handshake (multiple choices...)?
When I click that, the choices are two:
OpenNETCF.IO.Ports.Handshake
- and:
OpenNETCF.IO.Serial.Handshake
As the code in this unit deals with printing, I select "Ports" (rejecting "Serial" because of its yin/yanginess to "Parallel"). So it then adds back the using I had which it complained about (using OpenNETCF.IO.Ports)...and then it's back to the original err msg.
Yet I do have several OpenNETCF items in my References, namely:
OpenNETCF
OpenNETCF.Data
OpenNETCF.Drawing
OpenNETCF.Net
OpenNETCF.Phone
OpenNETCF.VisualBasic // I don't know why, this is a C# project
OpenNETCF.Web.Services2
OpenNETCF.Windows.Forms
OpenNETCF.WindowsCE.Forms
OpenNETCF.Xml
What could possibly cause this chicken-and-egg tail-chasing exercise in frustration?
Odder yet, I get, "The type or namespace name 'Windows' does not exist in the class or namespace 'OpenNETCF' (are you missing an assembly reference?)" pointing to this using in another .cs file:
using OpenNETCF.Windows.Forms;
...and yet that using is grayed out as being unused at any rate, but when I comment it out, I get a lot of other errors purportedly because it's gone, such as on this line:
IntPtr hwnd = OpenNETCF.Win32.Win32Window.GetCapture();
The type or namespace name 'Win32Window' does not exist in the class or namespace 'OpenNETCF.Win32' (are you missing an assembly reference?)
UPDATE
In another episode of "Well Flip My Bits!" I just now compiled, got those err msgs about not being able to reconcile this line of code with what is installed and configured, etc., scrolled up to see that the "using" it was supposedly missing was there, compiled again, and now it compiles fine. What the blue blazes?!?!?!?

This sounds like a problem you see when you are building a project for a "Client Profile" .net version while referencing assemblies that are not supported in client profile.
Try changing your project's build settings to use a .net framework version that is not "Client Profile".

One can use the namespace using inside class also, so consider moving it there, if there are classes that use both than use the full name as in OpenNETCF.IO.Ports.Handshake handshake = new OpenNETCF.IO.Ports.Handshake()
And for the class using namespace:
using System;
namespace MyNamespace
{
using OpenNETCF.IO.Ports;
//...
}

Unable to find the enum reference which is declared in same namespace in .net 3.5

I have created a class library project which has number of classes and enums. All are declared in same name space. However, while compiling the class library itself some other classes/methods reports error that not fininding the reference to perticular enums. I have declared enum as public.
namespace CommonInterfaces
{
public enum SettingsType
{
EnumType1,
EnumTYpe2,
EnumType3
}
}
namespace CommonInterfaces
{
public interface IPlayer
{
void Add(SettingsType type); <-- Error occured.
}
}
I tried giving full qualified name like CommonInterfaces.SettingsType but still it did not resove the problem. The exact error is
Error 1 The type or namespace name 'SettingsType' does not exist in the namespace 'CommonInterfaces'(are you missing an assembly reference?)
How to resolve the error?

Maybe its nested in other class? Then u have to use it like this: OtherClass.EnumName. Its only idea i have now. Such error could be solved only by knowing ur source code or at least where u define Enum and where it cannot be found.

i ran into this problem while using xamarin in vs2019. i cleaned and rebuilt solution again and again but didnt work then i restarted visual studio and problem gone.

I ran into this problem in VS2019. Restarting Visual Studio solved the problem.