C# – the difference between Convert.ToBoolean(string) and Boolean.Parse(string)

booleancparsing

What is the difference between the two methods

Convert.ToBoolean()

and

Boolean.Parse()?

Is there any reason to use one or the other?

Additionally, are there any other type.Parse() methods that I should watch out for?

Thanks,

Matt

Best Answer

Convert.ToBoolean(string) actually calls bool.Parse() anyway, so for non-null strings, there's no functional difference. (For null strings, Convert.ToBoolean() returns false, whereas bool.Parse() throws an ArgumentNullException.)

Given that fact, you should use bool.Parse() when you're certain that your input isn't null, since you save yourself one null check.

Convert.ToBoolean() of course has a number of other overloads that allow you to generate a bool from many other built-in types, whereas Parse() is for strings only.

In terms of type.Parse() methods you should look out for, all the built-in numeric types have Parse() as well as TryParse() methods. DateTime has those, as well as the additional ParseExact()/TryParseExact() methods, which allow you specify an expected format for the date.

This is the style that Microsoft tends to use in their examples.

It appears that the guidance in this area may have changed, as StyleCop now enforces the use of the C# specific aliases.

C# – the difference between const and readonly in C#

Apart from the apparent difference of

having to declare the value at the time of a definition for a const VS readonly values can be computed dynamically but need to be assigned before the constructor exits.. after that it is frozen.
const's are implicitly static. You use a ClassName.ConstantName notation to access them.

There is a subtle difference. Consider a class defined in AssemblyA.

public class Const_V_Readonly
{
  public const int I_CONST_VALUE = 2;
  public readonly int I_RO_VALUE;
  public Const_V_Readonly()
  {
     I_RO_VALUE = 3;
  }
}

AssemblyB references AssemblyA and uses these values in code. When this is compiled:

in the case of the const value, it is like a find-replace. The value 2 is 'baked into' the AssemblyB's IL. This means that if tomorrow I update I_CONST_VALUE to 20, AssemblyB would still have 2 till I recompile it.
in the case of the readonly value, it is like a ref to a memory location. The value is not baked into AssemblyB's IL. This means that if the memory location is updated, AssemblyB gets the new value without recompilation. So if I_RO_VALUE is updated to 30, you only need to build AssemblyA and all clients do not need to be recompiled.

So if you are confident that the value of the constant won't change, use a const.

public const int CM_IN_A_METER = 100;

But if you have a constant that may change (e.g. w.r.t. precision).. or when in doubt, use a readonly.

public readonly float PI = 3.14;

Update: Aku needs to get a mention because he pointed this out first. Also I need to plug where I learned this: Effective C# - Bill Wagner

Best Answer

Related Solutions

C# – the difference between String and string in C#

This is the style that Microsoft tends to use in their examples.

C# – the difference between const and readonly in C#

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