# How to convert a number from Decimal to Binary using recursion in C#?

To get the binary of Decimal, using recursion, firstly set the decimal number −

int dec = 30;

Now pass the value to a function −

public int displayBinary(int dec) {
}

Now, check the condition until the decimal value is 0 and using recursion get the mod 2 of the decimal num as shown below. The recursive call will call the function again with the dec/2 value −

public int displayBinary(int dec) {
int res;
if (dec != 0) {
res = (dec % 2) + 10 * displayBinary(dec / 2);
Console.Write(res);
return 0;
} else {
return 0;
}
}

The following is the complete code −

## Example

Live Demo

using System;

public class Program {
public static void Main(string[] args) {
int dec;
Demo d = new Demo();
dec = 30;
Console.Write("Decimal = "+dec);
Console.Write("Binary of {0} = ", dec);
d.displayBinary (dec);
Console.Write("");
}
}
public class Demo {
public int displayBinary(int dec){
int res;
if (dec != 0) {
res = (dec % 2) + 10 * displayBinary(dec / 2);
Console.Write(res);
return 0;
} else {
return 0;
}
}
}

## Output

Decimal = 30
Binary of 30 = 11110

Updated on: 22-Jun-2020

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