CODEWITHSUNDEEP
c#c++
Sss
Sss

Reputation: 1529

How to define constructor outside the class in c#

I am new to c# and just switched from c++ to c#. I was doing something like this in c++:

Class A
{
 public : A(char *argv);//declaration of constructor
}

then in main i was doing like this:

int main(int argc, char **argv)
{
 A Obj(argv[1]);
}

then definition of constructor i do like this :

A::A(char * argv) 
{
 //Here i use this command line argument argv which contains a file.
}

I tried to write equivalent code in c# which is as follows:

using System;
using System.IO;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace shekhar_final
 {
    class Huffman 
    {
    public  int data_size,length,i,is_there, total_nodes;
    string code;
    Huffman(char  *args);
    }

        public   Huffman(char  *args) //called from MyClass  Line:16
        {
            using (var stream = new BinaryReader(System.IO.File.OpenRead(args[0])))  //Line : 18
            {
                while (stream.BaseStream.Position < stream.BaseStream.Length)
                {
                    byte processingValue = stream.ReadByte();
                }
            }
        }

    public class MyClass 
    {
        public static void Main(string[] args)
        {       
         Huffman ObjSym =new Huffman(args);//object creation
        }
    }
}// Line:34

The couple of errors i got are ://I have indicated the line corresponding to the errors in my code

shekhar_c#.cs(16,25): error CS1525: Unexpected symbol `Huffman', expecting `class', `delegate', `enum', `interface', `partial', or `struct'
shekhar_c#.cs(18,33): error CS1530: Keyword `new' is not allowed on namespace elements
shekhar_c#.cs(18,36): error CS1525: Unexpected symbol `BinaryReader', expecting `class', `delegate', `enum', `interface', `partial', or `struct'
shekhar_c#.cs(18,79): warning CS0658: `value' is invalid attribute target. All attributes in this attribute section will be ignored
shekhar_c#.cs(34,1): error CS8025: Parsing error
Compilation failed: 4 error(s), 1 warnings

Could you please help me in writing c# equivalent of this c++ (removing these errors). Extra guidance are also welcome because i am beginner to c#.

Upvotes: 1

Views: 1921

Answers (6)

T McKeown
T McKeown

Reputation: 12857

C# requires constructors to be defined within the class:

using System;
using System.IO;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace shekhar_final
{
    public class Huffman{

    public  int data_size,length,i,is_there, total_nodes;
    string code;

     public   Huffman(string[]  args) //called from MyClass  Line:16
     {
         using (var stream = new BinaryReader(System.IO.File.OpenRead(args[0])))  //Line : 18
         {
             while (stream.BaseStream.Position < stream.BaseStream.Length)
             {
                 byte processingValue = stream.ReadByte();
             }
         }
      }
    }

   public class MyClass 
   {
       public static void Main(string[] args)
       {       
         Huffman ObjSym =new Huffman(args);//object creation
       }
   }
}// Line:34

Upvotes: 1

LB2
LB2

Reputation: 4860

In C#, declarations and implementations go together:

namespace shekhar_final
{
    class Huffman 
    {
        public int DataSize {get; set;}
        public int Length {get; set;}
        public int I {get;set;}
        public int IsThere {get;set;}
        public int TotalNodes {get;set;}
        private string code;

        public Huffman(string[] args) //called from MyClass  Line:16
        {
            using (var stream = new BinaryReader(System.IO.File.OpenRead(args[0])))  //Line : 18
            {
                while (stream.BaseStream.Position < stream.BaseStream.Length)
                {
                    byte processingValue = stream.ReadByte();
                }
            }
        }
    }

    public class MyClass 
    {
        public static void Main(string[] args)
        {       
           Huffman objSym = new Huffman(args);//object creation
        }
    }
}// Line:34

Upvotes: 3

Wrongway
Wrongway

Reputation: 47

The main phlosophy between C# and C++ are different. In C++ you have a header file and an implementation file. In C#, everthing needs to be within a class. So, you declare the constructor to the class and put the implementation within it.

class funny {
    public funny() {
     ...  add your constructor stuff here
    }
    ... other stuff ...
 }

Upvotes: 2

rerun
rerun

Reputation: 25505

In c# you do not separate declaration and definition. There is no such concept as declaration in c# since all the types exist together in an assembly. If you wish to use multiple files in c3 for classes you can use the concept of partial classes.

Upvotes: 1

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726669

Unlike C++ where you have a choice of combining the declaration and the definition of a member function in the header, or placing the declaration in the header and the implementation in the cpp file, in C# there is no such choice: if a function has a body (i.e. it is not abstract), the body needs to be part of the declaration:

class Huffman 
{
    public  int data_size,length,i,is_there, total_nodes;
    string code;
    Huffman(string args) {
        using (var stream = new BinaryReader(System.IO.File.OpenRead(args)))
        {
            while (stream.BaseStream.Position < stream.BaseStream.Length)
            {
                byte processingValue = stream.ReadByte();
            }
        }
    }
}

Upvotes: 3

Polynomial
Polynomial

Reputation: 28316

You don't define methods ahead of time in C# - they're defined within the class itself. Try this instead:

class Huffman 
{
public  int data_size,length,i,is_there, total_nodes;
string code;

    public Huffman(char *args) //called from MyClass  Line:16
    {
        using (var stream = new BinaryReader(System.IO.File.OpenRead(args[0])))  //Line : 18
        {
            while (stream.BaseStream.Position < stream.BaseStream.Length)
            {
                byte processingValue = stream.ReadByte();
            }
        }
    }
}

public class MyClass 
{
    public static void Main(string[] args)
    {       
         Huffman ObjSym =new Huffman(args); //Here is the error
    }
}

Upvotes: 2

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