Friday, July 29, 2005
Via Virtual Earth - Homepage
RSA Public/Private key encryption/decryption in .NET
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Thursday, July 28, 2005
Q: How do I write a method that accepts a variable number of parameters?
Q: How do I write a method that accepts a variable number of parameters?
A: Languages like C and C++ have always offered some means for using and creating functions capable to accept a variable number of parameters. The most widely known example of a function which takes a variable number of parameters is printf():
int printf(char *format, …); // the ellipsis means "variable number of params"
Using this function is pretty easy:
printf("Hello, world\n");
printf("The sum of %d and %d is %d\n", a, b, a+b);
However, the creation of such functions in these languages relays on a set of predefined macros and is not particularly elegant or intuitive.
C# offers an elegant solution to this problem through parameter arrays. A parameter array is a single-dimensional array included as the last parameter in the parameter list of a method:
public string Concat(string separator, params string[] strings)
{
string result = "";
for (int i = 0; i <>
{
if (i > 0)
result += separator;
result += strings[i];
}
return result;
}
Such a function can be called in two different ways:
a) Passing the function an array instance argument:
string[] names = { "Anders", "Eric", "Scott", "Duncan" };
MessageBox.Show(Concat("+", names) + " = great team");
b) Using zero or more type-compatible arguments for the parameter array:
MessageBox.Show(Concat("+", "Anders", "Eric", "Scott", "Duncan") +
" = great team");
In this case, the invocation will create an array from the supplied arguments and use it as the actual argument.
Thanks to the unified .NET type system, object[] can be used as “common denominator” for arguments of different types:
public int SumTheIntegers(params object[] list)
{
// sum all the integers included in list
int sum = 0;
foreach (object o in list)
if (o.GetType() == typeof(int))
sum += (int) o;
return sum;
}