Default or optional Parameters in C#

[indian143]

Hi, We have default parameters in C++ like at the time of function definition we can give some default value to a parameter. Is there anyhting similar in C#. Because when I gave like in the below line it was giving me error in the C#, can I use this thing in the C#

public static void sample(int i=100, string s=string.Empty, bool b=true)
{
///Something
}

Thanks & Regards, Md. Abdul Aleem NIIT technologies

[Rob Philpott]

Default parameters have been added in .NET4 (I'm pretty sure) otherwise you'll have to supply the default in the calling method.

Regards, Rob Philpott.

[Luc Pattyn]

yep. 4.0 is what you want (and that may mean Visual Studio 2010!). :)

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[PIEBALDconsult]

C# 4.0

[indian143]

Ok. Thanks guys I am still using VS 2008 so it wont work for me.

Thanks & Regards, Md. Abdul Aleem NIIT technologies

[Abhinav S]

You need to use .Net 4.0.

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[RaviRanjanKr]

Of-course C# 4.0 , navigate the given link to get better clarification over optional parameter. Click Me[^] :)

[Roger Wright]

You can accomplish a similar effect by defining several versions of the same function, each with a different signature:

public static void sample(int i, string a)
{
bool b= true;
//more stuff
}

public static void sample(int i, bool b)
{
string s = string.Empty;
//more stuff
}

public static void sample(string a, bool b)
{
int i = 100;
//more stuff
}

etc... If I remember my reading correctly, at run time the calling statement will be matched to the version with matching parameters, and the function will fill in the missing values with the predefined defaults. Of course, I may be a complete idiot - I'm fairly new to C#. But it's what I would try if I really needed to do this. :)

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[deepakshukla79]

You can use optional parameter . you can this by this way class Program { static void Main(string[] args) { Console.WriteLine(Sum(1, 2, 3).ToString()); Console.WriteLine(Sum( 2, 3).ToString()); Console.ReadLine(); } static int Sum(params int[] li) { int sum=0; for ( int i = 0 ; i < li.Length ; i++ ) { sum+=li[i]; } return sum; } }

[Hiren solanki]

You've provided a way which can be only applicable to Integer, Try to expand it for all type of object passed in method. Like instead of receiving data only in a array of int[], Receive it in object[]. and further check of every item in array whether it's bool,string,object of custom class,float,decimal. That would be quite cumbersome, optional parameter is the good way , I guess.

Regards, Hiren.

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[Gary Wheeler]

I usually implement that pattern as follows in C# 3.5:

public static void sample(int i, string a)
{
_sample(i,false,true,a);
}
public static void sample(int i, bool b)
_sample(i,false,b,string.Empty);
}
public static void sample(string a, bool b)
{
_sample(100,false,b,a);
}
private static void _sample(int i,bool a,bool b,string a_string)
{
// implement 'sample' operation
}

Software Zen: delete this;

[Spectre_001]

Not exactly elegant but...

public static void sample(int i, string s, bool b)
{
if (i == default(int)) { i = 100; }
if (s == default(string)) { s = string.Empty; }
if (b == default(bool)) { b = true; }

// The rest of your method...

}

Works in .NET Framework 3.5.

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[PIEBALDconsult]

C# 4 !

[Hari Om Prakash Sharma]

visual studio 2010

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[hground]

VB .NET has had optional parameters for some time :) Looks like it took C# a while to catch up :) (Yeah - I know! I shouldn't throw rocks at hornet's nests, but sometimes you just can't resist!)

[jlafay]

That's possible in C# 4, and the same syntax applies. -jeff

[grgran]

As already pointed out, optional, default and named parameters are available in .NET 4.0 Interestingly, if you do use them the code analysis tool slaps your hand about it, requesting that you create overloads with the defaults set in method. G

[Paladin2000]

No, you can't set default values. But you can use an overload to accomplish something similar.

public static void sample(int i, string s, bool b)
{
///Something
}

public static void sample()
{
sample(100, string.Empty, true);
}

public static void sample(int i)
{
sample(i, string.Empty, true);
}

///Etc...

[djdanlib 0]

Wait, how does that even work? I've never even heard of something like that. I am intrigued. Is this what you're doing? http://msdn.microsoft.com/en-us/library/xwth0h0d%28v=VS.80%29.aspx[^]

[Spectre_001]

Yes, it just returns the framework's default value for the type specified.

Kevin Rucker, Application Programmer QSS Group, Inc. United States Coast Guard OSC Kevin.D.Rucker@uscg.mil "Programming is an art form that fights back." -- Chad Hower