Class EnvTokenExpander

This class is implemented as a very lean Singleton.

Inheritance
System.Object
EnvTokenExpander
Namespace: WizardWrx.Core
Assembly: WizardWrx.Core.dll
Syntax
public class EnvTokenExpander : object

Fields

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ENV_STR_DLM

For reference, the character that delminits an environment string token is exposed as a public constant.

Declaration
public const char ENV_STR_DLM = null
Field Value
Type Description
System.Char

Properties

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Busy

Returns TRUE if the EnvTokenExpander is Busy, which means that a thread has acquired it, by calling its Acquire method.

Declaration
public bool Busy { get; }
Property Value
Type Description
System.Boolean
Remarks

By acquiring the EnvTokenExpander, a thread can shave a tad off the processing needed to find the first occurrance of a token, in order to extract it, if it intends to call ContainsEnvToken before calling ExtractEnvToken.

Methods

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Acquire()

Rather than have the caller lock the object, I provide this pair of methods that create a similar effect, by causing a competing caller of an object in a Frozen state to told to wait its turn.

Declaration
public bool Acquire()
Returns
Type Description
System.Boolean

TRUE, unless the object is already frozen by another thread.
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ContainsEnvToken(String)

Returns TRUE if the input string contains at least one environment string token.

Declaration
public bool ContainsEnvToken(string pstrIn)
Parameters
Type Name Description
System.String pstrIn

String to evaluate for presence of environment string tokens.
Returns
Type Description
System.Boolean

TRUE if the string contains at least one environment string token. Otherwise return FALSE.
Remarks

An environment string token is defined as a substring delimited by '%' charagers, which are symbolically represented by ENV_STR_DLM in this class.

Because this is a public method of a singleton, it cannot be marked Static. If it were so marked, it would lose access to the private storage that motivated me to finally sit down and figure out how to implement the Singleton pattern in C#.

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ExpandEnvironmentTokens(String, String)

Given a string that contains one or more environment string tokens, expand the tokens, returning the resulting string.

Declaration
public static string ExpandEnvironmentTokens(string pstrIn, string pstrDefault = null)
Parameters
Type Name Description
System.String pstrIn

String to parse and expand environment string tokens.
System.String pstrDefault

Optional string to return as default if an undefined (empty) environment variable is encountered in input string pstrIn.
Returns
Type Description
System.String

The return value is string pstrIn with its environment tokens expanded.
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ExtractEnvToken(String)

If the input string contains an enviroment token, extract and return it.

Declaration
public string ExtractEnvToken(string pstrIn)
Parameters
Type Name Description
System.String pstrIn

String from which to extract an environment variable token.
Returns
Type Description
System.String

String containing the token, minus its delimiters.
Remarks

An environment string token is defined as a substring delimited by '%' charagers, which are symbolically represented by ENV_STR_DLM in this class.

Since this method returns the string without its delimiters, pass it to static method TokenizeEnvVarName to convert it to a string that can be passed into a Replace method, to replace the token with its value, which you got by calling Environment.GetEnvironmentVariable.

Because this is a public method of a singleton, it cannot be marked Static. If it were so marked, it would lose access to the private storage that motivated me to finally sit down and figure out how to implement the Singleton pattern in C#.

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Free()

Rather than have the caller lock the object, I provide this pair of methods that create a similar effect, by causing a competing caller of an object in a Frozen state to be thrown and exception.

Declaration
public bool Free()
Returns
Type Description
System.Boolean

Always True.
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GetTokenExpander()

All classes that want to call methods on this object must first call this method.

Declaration
public static EnvTokenExpander GetTokenExpander()
Returns
Type Description
EnvTokenExpander

A reference to the single instance of this object, which all consumers share.
Remarks

This pseudo-constructor must be declared static. Its only real job is to return a reference to itself, personified as _TheInstance.

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TokenizeEnvVarName(String)

Given a string, assumed to be the name of an environment string, return it with the expected escape ("quote") characters appended to both ends.

Declaration
public static string TokenizeEnvVarName(string pstrIn)
Parameters
Type Name Description
System.String pstrIn

String to turn into an environment variable token.
Returns
Type Description
System.String

String pstrIn, with the escape characters (%) appended to both ends.
Remarks

Use this method to turn the output of ExtractEnvToken into a string that can be fed to a Replace method to substitute the value of the environment variable for its token.