.Net Parse versus Convert

Question

In .Net you can read a string value into another data type using either <datatype>.parse or Convert.To<DataType>.

I'm not familiar with the fundamentals of parse versus convert so I am always at a loss when asked which one is better/faster/more appropriate.

So - which way is best in what type of circumstances?

Answer 1

The Convert.ToXXX() methods are for objects that might be of the correct or similar type, while .Parse() and .TryParse() are specifically for strings:

//o is actually a boxed int
object o = 12345;

//unboxes it
int castVal = (int) 12345;

//o is a boxed enum
object o = MyEnum.ValueA;

//this will get the underlying int of ValueA
int convVal = Convert.ToInt32( o );

//now we have a string
string s = "12345";

//this will throw an exception if s can't be parsed
int parseVal = int.Parse( s );

//alternatively:
int tryVal;
if( int.TryParse( s, out tryVal ) ) {
    //do something with tryVal 
}

If you compile with optimisation flags TryParse is very quick - it's the best way to get a number from a string. However if you have an object that might be an int or might be a string Convert.ToInt32 is quicker.

Answer 2

Here's an answer for you:

http://www.dotnetspider.com/forum/ViewForum.aspx?ForumId=77428

Though I think in modern versions of .NET, the best thing to do is use TryParse in any case, if there's any doubt that the conversion will work.

Answer 3

I'm a big fan of TryParse, since it saves you a lot of headache of error catching when there's a chance the value you're going to parse is not of the appropriate type.

My order is usually:

• Parse (if I can be sure the value will be the right type, and I do try to ensure this)
• TryParse (if I can't be sure, which happens whenever user input is involved, or input from a system you cannot control)
• Convert (which I think I have not used since I started using Parse and TryParse, but I could be wrong)