c# - Why does the source code for the Guid constructor contain the line "this = Guid.Empty"? -

c# - Why does the source code for the Guid constructor contain the line "this = Guid.Empty"? -

if source code constructor of guid(string) in .net 4.5.2 source code follows:

public guid(string g) { if (g==null) { throw new argumentnullexception("g"); } contract.endcontractblock(); = guid.empty; guidresult result = new guidresult(); result.init(guidparsethrowstyle.all); if (tryparseguid(g, guidstyles.any, ref result)) { = result.parsedguid; } else { throw result.getguidparseexception(); } }

the question purpose of line this = guid.empty;?

from can see if string g can parsed in tryparseguid method this assigned. if can't exception thrown.

suppose wrote:

var guid = new guid("invalidguid");

this cause exception , value of guid undefined assume. why need assign this guid.empty?

this more matter of style else - functionally it's superfluous , compiler may optimize away assignment guid.empty in generated code.

defensive coding recommends variable should have initial value explicitly assigned. why? because reduces ambiguity, unfamiliar details of given programming language/platform. illustration 1 might ask:

what default value of guid? should new guid? should zero's? should other indeterminate state?

in stating:

guid id = guid.empty;

all these questions answered reading code , without having resort reading documentation and/or source. further, it's explicit variable id starts out beingness empty indicates reader it'll have value set later in code.

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