(string)reader[0] vs Convert.ToString(reader[0])

Question

what's better

var s =  (string)reader[0]  

or

var s = Convert.ToString(reader[0])

?

Answer 1

I would guess reader[0].ToString();

Answer 2

If reader[0] is actually a string, then the (string)reader[0].

It's clearer and most probably faster (unless the compiler does some magical optimization I don't know about).

Answer 3

what about

reader[0].ToString();

Answer 4

var s =  (string)reader[0]  

will give you a class cast exception if it can't be cast as a string, whereas

var s = Convert.ToString(reader[0])

will handle it more gracefully and you will get null if it can't be converted. This will also handle more types of object for reader[0] as the other method will only allow casts where the type can be cast to a string, whereas this will support any type which the Convert Class can handle. Which I assume is more. But may not be...

Answer 5

I'd say reader.GetString(0)

Answer 6

This is faster, about ~30% faster in my testing:

var s =  (string)reader[0];

This, however, won't blow up when it's null:

var s = Convert.ToString(reader[0]);

Answer 7

How about reader.GetString(0);?

Answer 8

// Conveys that you are sure that reader[0] is a string and 
// if it's not you probably have bigger problems 
// than the resulting exception
var s =  (string)reader[0];

// Conveys that you are hoping that reader[0] is convertible to a string
var s = Convert.ToString(reader[0])

So it's probably a matter of choosing taking in consideration the context.

Answer 9

I would go with

reader[0].ToString();

Answer 10

Why did nobody considered the readability and maintainability?

I know the author asks about:

var s =  (string)reader[0]      
or    
var s = Convert.ToString(reader[0])

But what about:

string s = reader["Fieldname"].ToString(); 

thats more readable and more safe if you exchange/delete/add columns and the index is changing... this is for sure more worth.

One guy said the hard cast is 30% faster. Well 30% of 1 ms are 1,333 ms ? surely not 30% of the whole data fetching.