command line in C#

Question

I have a tool which I want to run from my command prompt.

The code is as

    static void Main(string[] args)
    {

        string User;            
        if (args[0].Length  != 0)
        {
             User = args[0];
        }
        else
        {
        Console.Write("Please Enter the Username");
        User = Console.ReadLine();
        }

If I didnt give the username or the first argument after my 'tool.exe' in command prompt, it throws an exception like "Index was outside the bounds of the array"

I want ouptut as, if I didnt give argument - it should prompt me to give the username. please help me out.

Answer 1

args is an array, and is what you should be checking for length. When you check args[0].Length you're actually assuming there's atleast one element in the array already and thus you're checking Length of the first item.

Try

if (args.Length != 0)

instead, which checks the length of the array of command line parameters.

Answer 2

You don't want to call Length on the item.

            \/ Change here
     if (args.Length  != 0)
    {
         User = args[0];
    }
    else
    {
    Console.Write("Please Enter the Username");
    User = Console.ReadLine();
    }

Answer 3

You need to change the if to:

static void Main(string[] args)
{

    string User;            
    if (args.Length  != 0) // Change from args[0] to args
    {
         User = args[0];
    }
    else
    {
    Console.Write("Please Enter the Username");
    User = Console.ReadLine();
    }
}

After this call make sure you do a string.IsNullOrEmpty(User) beforen you use it.

Answer 4

do this

static void Main(string[] args)
{

string User;            
if (args.Length > 0)
{
     User = args[0];
}
else
{
Console.Write("Please Enter the Username");
User = Console.ReadLine();
}
}

Answer 5

You have to check length of argument array, ie the number of arguments. Currently you are checking the size of args[0].

if (args.Length  != 0)
{
  // command have some params
}
else
{
 // command have no params
}

Answer 6

Just replace the following line:

if (args[0].Length != 0)

With the following code:

if(arg.Length !=0) <br>

In your code, you have referenced item 0 in the args array and then check its length.
Since you want to check the array length, use the Length property of the array itselft

Answer 7

By doing like this you are looking on the first element in the collection string[].

if (args[0].Length  != 0)

This will give a exception if there isn't any arguments. Correct statement are the following if you want to check if there is any arguments.

if (args.Length  != 0)
//Or this
if (args.Any())

Observe that the Any() is a part of the namespace System.Linq.