optional parameter write methods

Hemant Sharma

12y1.5k.NET

Hi all i am a absolute beginner of c#5.0 and i want to understand how the Console.Writeline is different for optional parameters e.g

class test
{
static void Prg(int a=0,int b=0,int c=0,int d=0)
{Console.Writeline(a,b,c,d);}
static void Main()
{
Prg();
}

i want to print values for a,b,c,d as 0 0 0 0 in o/p

but iit shows error as 'overload method has some invalid arguments.

tell me methods for Console.Write() for this code,thanks in advance.

6 Replies

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Khan Abrar Ahmed12y ago
Accepted answer
Hi you can use this for optional parameter
Console.WriteLine("{0}, {1}, {2},{3}",a,b,c,d);
Vulpes12y ago
The Console.WriteLine() method has 19 overloads but only one of them can deal with an arbirary number of parameters, namely:

WriteLine(string format, params Object[] arg)

Basically, the C# compiler first tries to fit one of the overloads which take a fixed number of parameters, depending on their type and number, to what you have written in your source code. If it can't find a match, it then tries the above overload and if that doesn't match either it issues an error.

So, whilst this didn't match any overload:

Console.Writeline(a, b, c, d);

this one matched the overload which takes an arbitrary number of parameters:

Console.WriteLine("{0}, {1}, {2}, {3}", a, b, c, d);

because, of course, an object array can hold values of any type including int.

The first parameter formats the parameters by separating them with a space and a comma.

{0}, {1}, {2} etc. are what's called 'placeholders' for the subsequent parameters.
Hemant Sharma12y ago
I wants a single instruction in Prg method to print all optional parameter's values.
Khan Abrar Ahmed12y ago
HI, can you please let us know what output you want like 0,0,0,0 or
0
0
0
0
Hemant Sharma12y ago
But i found Console.Writeline(a+","+b); if there are only two optional parameters a,b and it works but for all a,b,c,d i don't know,i saw that e.g in optional parameters.
Khan Abrar Ahmed12y ago
hi you can use two thing.

class test
{
static void Prg(int a=0,int b=0,int c=0,int d=0)
{
Console.Writeline(a.tostring());

Console.Writeline(b.tostring());

Console.Writeline(c.tostring());

Console.Writeline(d.tostring());}
static void Main()
{
Prg();
}

or
```
Console.WriteLine("{0}, {1}, {2},{3}", // <-- This is called a format string.     a,                      // <-- These are substitutions.     b,     c,d);
```