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.NET / C# Troubleshooting

The name 'NNNN' does not exist in the current context (C#)

Symptom:

When compiling a C# application the compiler generates the following error:

The name 'NNNN' does not exist in the current context

where 'NNNN' is the name of a variable.

If you are using VB.Net then the error message is slightly different (but means the same thing):

'NNNN' is not declared. It may be inaccessible due to its protection level.

in this case please refer to the VB.Net version of this article "NNNN is not declared".

Possible Cause 1: (see also Possible Cause 2 below)

The compiler does not recognise the variable 'NNNN'. This is either because the variable name is miss-spelt or because the compiler could not find a corresponding definition.

Remedy:

• A common cause is a simple misspelling where the identifier is used. For example:

int number;
numbr = 1;

Here the identifier is defined as 'number' but used in the code as 'numbr'. The solution is to correct the spelling.

• If the name is referring to an identifier then it may be that the reference simply needs to be qualified. For example:

using System.Web.HttpContext;

class Example
    string ExampleFunc()
    {
        return Application["name"];
.
.
[Error] Name 'Application' is not declared.

Try replacing "Application" with "Current.Application".

• The most common cause is that the namespace that defines the name is missing. Identify and import the required namespace - the table below should help.

  For example, with the error:

  The name 'Directory' does not exist in the current context

  The missing namespace is System.IO, so the solution is to add:

  using System.IO;

  at the top of the file.

  The following table (which is not exhaustive) lists identifiers together with the namespace and any qualification that might typically be required:

  Name	Namespace	Common Qualified Name
  Abs	Math	Math.Abs
  AnchorStyles	System.Windows.Forms
  Application	System.Windows.Forms For Windows forms applications.
  	System.Web.HttpContext For web applications.	Current.Application
  ApplicationDeployment	System.Deployment.Application
  Assembly	System.Reflection
  CultureInfo	System.Globalization
  Cache	System.Web.Caching
  ConfigurationManager	System.Configuration Also ensure that project contains reference to System.Configuration.dll
  Current	System.Web.HttpContext
  Debug	System.Diagnostics
  Debugger	System.Diagnostics
  Directory	System.IO
  Dns	System.Net
  Encoding	System.Text
  EventLog	System.Diagnostics
  File	System.IO
  HtmlEncode	System.Web.HttpUtility
  HttpContext	System.Web
  HttpRuntime	System.Web
  HttpUtility	System.Web
  ImageFormat	System.Drawing.Imaging
  Marshal	System.Runtime.InteropServices
  NormalizationForm	System.Text
  Parallel	System.Threading.Tasks
  Process	System.Diagnostics
  Regex	System.Text.RegularExpressions
  Request	System.Web.HttpContext	Current.Request
  Round	Math	Math.Round
  SecurityMode	System.ServiceModel
  SecurityZone	System.Security
  Server	System.Web.HttpContext	Current.Server
  ServicePointManager	System.Net
  SslPolicyErrors	System.Net.Security
  SmptMail	System.Web.Mail
  ThreadPool	System.Threading
  UnicodeCategory	System.Globolization
  UrlDecode		HttpContext.Current.Server.UrlDecode
  User		HttpContext.Current.User

It is my intention to add to this table over time.

Possible Cause 2:

A less likely cause is that the project itself lacks a reference to the necessary library. This can arise when (for example) creating a class library and using web namespaces, for example:

The name 'HttpRuntime' does not exist in the current context

or

The name 'HttpContext' does not exist in the current context

even though the line "using System.Web" is included.

Remedy

Add the reference to the project:

1. Expand the "References" shown in the solution explorer for the project.
2. Check that the required namespace is listed under "References".

   The required reference is listed in the table above (given under "Possible Cause 1"). If it is not listed then right click on "References" and select "Add reference...". In the "Add Reference" dialog box that will then appear, the reference you require will probably be on the ".NET" tab.

For example, the solution to "HttpRuntime (or HttpContext) does not exist" (even though "Imports System.Web" is included in the file) is to ensure that "System.Web" is listed as one of the project References.

These notes are believed to be correct for C# for the .NET 4, .NET 3, .NET 2 and .NET 1.1 frameworks, and may apply to other versions as well.

For the corresponding VB.NET version of this article please see "NNNN is not declared".