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.NET / VB.Net Troubleshooting

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'NNNN' is not declared (VB.NET)

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Symptom:

When compiling a VB.Net application the compiler generates the following error:

error BC30451: 'NNNN' is not declared. It may be inaccessible due to its protection level.

Visual Studio 2010 simply gives the error:

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

or with older versions of Visual Studio (i.e. up to and including Visual Studio 2008): 

Name 'NNNN' is not declared.

where 'NNNN' is the name of a variable.

If you are using C# then the error message is slightly different (but means the same thing):

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

in this case please refer to the C# version of this article "The name NNNN does not exist in the current context".

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 misspelt 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:

dim number as Integer
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:

Imports System.Web.HttpContext
Module Example
    Function ExampleProc() as String
        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:

  Name 'Directory' is not declared.

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

  Imports 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
  BindingFlags	System.Reflection
  CultureInfo	System.Globalization
  Cache	System.Web.Caching
  CipherMode	System.Security.Cryptography
  ConfigurationManager	System.Configuration Also ensure project contains reference to System.Configuration.dll
  Current	System.Web.HttpContext
  Debug	System.Diagnostics
  Debugger	System.Diagnostics
  Dns	System.Net
  Directory	System.IO
  Encoding	System.Text
  EventLog	System.Diagnostics
  File	System.IO
  FormsAuthentication	System.Web.Security
  HostingEnvironment	System.Web.Hosting
  HtmlEncode	System.Web.HttpUtility
  HttpContext	System.Web Also ensure project contains reference to System.Web.
  HttpRuntime	System.Web
  HttpStatusCode	System.Net
  HttpUtility	System.Web
  ImageFormat	System.Drawing.Imaging
  Marshal	System.Runtime.InteropServices
  NormalizationForm	System.Text
  PaddingMode	System.Security.Cryptography
  Parallel	System.Threading.Tasks
  Path	System.IO
  Process	System.Diagnostics
  Regex	System.Text.RegularExpressions
  Request	System.Web.HttpContext	Current.Request
  Round	Math	Math.Round
  SecurityElement	System.Security
  SecurityMode	System.ServiceModel
  SecurityZone	System.Security
  Server	System.Web.HttpContext	Current.Server
  ServicePointManager	System.Net
  SmptMail	System.Web.Mail
  SslPolicyErrors	System.Net.Security
  Stopwatch	System.Diagnostics
  ThreadPool	System.Threading
  UnicodeCategory	System.Globolization
  UrlDecode		HttpContext.Current.Server.UrlDecode
  User		HttpContext.Current.User
  UTF8Encoding	System.Text
  VirtualPathUtility	System.Web

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

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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:

Name 'HttpContext' is not declared

or

Name 'HttpRuntime' is not declared

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

Remedy

Add the reference to the project:

1. Right click the project in the solution explorer and select "properties".
2. On the "References" tab ensure that the required namespace is listed under "References" (do not confuse this with "Imported namespaces", the important thing is that it must be listed under "References".)

The necessary references are listed in the table above (shown under "Possible Cause 1"). For example the solution to "HttpContext (or HttpRuntime) is not declared" even though "Imports System.Web" is included in the file is to ensure that "System.Web" is listed as one of the project References.

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

For the corresponding C# version of this article please see "The name NNNN does not exist in the current context".