Using input parameter with Enum value

Question

Hi

Given the following code example

// Method declaration
private bool ValidRequest(RequestBase request, ResponseBase response, Validate validate)

// Condition statement
if ((Validate.ClientTag & validate) == Validate.ClientTag)

Validate is an Enum with a variable ClientTag that has a value of 0x0001 assigned.

Am I right in saying that given Validate.ClientTag is an Enum, the assignment operator cannot be used to Set the input parameter validate. As a result the & operator needs to be used instead?

In addition the expression (Validate.ClientTag & validate) has to be encapsulated into its own parenthesis within the if statement due to the mismatch of types ClientTag and bool?

Thanks

Vulpes · Answer

What's probably happening here is that Validate is a 'flags' enum and the variable 'validate' could therefore contain a combination of distinct values - typically 1, 2, 4, 8 etc. This sort of code is used to find out whether Validate.ClientTag is one of those values. Suppose for example that 'validate' has a value of 3 which is a combination of 1 and 2. If you wanted to find out whether 1 (the value of Validate.ClientTag) is one of them you couldn't just do a simple equality test like the one below even though it would be perfectly valid C#: if (Validate.ClientTag == validate) because the condition would be false. Instead you have to 'and' validate with Validate.ClientTag and see whether the result is equal to Validate.ClientTag. The parentheses are in there because the == operator has a higher precedence than the & operator - so it wouldn't work properly without them.

Vulpes · Answer

Yes, the other members of the Validate enum are consistent with what I said about it being a 'Flags' enum. In fact there's even a member (All) which is defined as a combination of the other three members and so, if this member were passed into the method's 'validate' parameter, 'ANDing' it with Validate.ClientTag would yield Validate.ClientTag and so the 'if' condition would be true. You can in fact use ANY value of the underlying type (usually int) as an enum value, whether it corresponds with one of the defined values or not, simply by casting it to the enum type. However, this is normally poor programming practice and you should therefore stick to only assigning defined values to an enum variable. The request 'parameter' is of type RequestBase which I don't know anything about but it evidently has a ClientTag property of type string because "ABC123" is a string.

Guest User · Answer

Vulpes Further to your previous reply. Could you kindly answer another related question please. The Validate Enum has the following variables and values:- ClientTag = 0x0001, AccessToken = 0x0002, UserCredentials = 0x0004, All = ClientTag | AccessToken | UserCredentials Under the ValidRequest method declaration the first if statement looks like the one I showed previously ie if ((Validate.ClientTag & validate) == Validate.ClientTag) it then has another if statement as follows:- if (request.ClientTag != "ABC123") the value "ABC123" is declared in a Web.Config file There is another 2 declarations for the AccessToken and UserCredentials flags. My questions are:- Does the above still fit in with what you replied with? What type of value should I expect to see passed into the input parameter (Validate validate) I assume it could be anything? Are the values to each Enum variable simply just values that have no relation with the value that validate will receive? Thanks

Guest User · Answer

Thanks kindly Vulpes