How to Pad an Integer Number With Leading Zeroes in C#?

Given a Number N, the task is to pad this number with P number of leading zeros in C#.

Examples:

Input: N = 123 , P = 4
Output: 0123
  
Input: N = -3 , P = 5
Output: -00003

Method 1: Using string Format() method : The Format() method is used to replace one or more format items in the specified string with the string representation of a specified object.

Step 1: Get the Number N and number of leading zeros P.

Step 2: Convert the number to string and to pad the string, use the string.Format() method with the formatted string argument “{0:0000}” for P= 4.

val = string.Format("{0:0000}", N);

Step 3: Return the padded string.

Example :

C#

// C# program to pad an integer
// number with leading zeros
using System;

class GFG{

    // Function to pad an integer number
    // with leading zeros
    static string pad_an_int(int N, int P)
    {
        // string used in Format() method
        string s = "{0:";
        for( int i=0 ; i<P ; i++)
        {
            s += "0";
        }
        s += "}";

        // use of string.Format() method
        string value = string.Format(s, N);

        // return output
        return value;
    }

    // driver code
    public static void Main(string[] args)
    {
        int N = 123; // Number to be pad
        int P = 5; // Number of leading zeros

        Console.WriteLine("Before Padding: " + N);

        // Function calling
        Console.WriteLine("After Padding: " + pad_an_int(N, P));
    }
}

Output:

Before Padding: 123
After Padding: 00123

Method 2: Using ToString() method : The ToString() method is used to convert the numeric value of the current instance to its equivalent string representation.

Step 1: Get the Number N and number of leading zeros P.

Step 2: Convert the number to string using the ToString() method and to pad the string use the formatted string argument “0000” for P= 4.

val = N.ToString("0000");

Step 3: Return the padded string.

Example :

C#

// C# program to pad an integer
// number with leading zeros
using System;

public class GFG{

    // Function to pad an integer number
    // with leading zeros
    static string pad_an_int(int N, int P)
    {
        // string used in ToString() method
        string s = "";
        for( int i=0 ; i<P ; i++)
        {
            s += "0";
        }

        // use of ToString() method
        string value = N.ToString(s);

        // return output
        return value;
    }

    // driver code
    public static void Main(string[] args)
    {
        int N = 123; // Number to be pad
        int P = 5; // Number of leading zeros

        Console.WriteLine("Before Padding: " + N);

        // Function calling
        Console.WriteLine("After Padding: " + pad_an_int(N, P));
    }
}

Output:

Before Padding: 123
After Padding: 00123

Method 3: Using PadLeft() method : The PadLeft() method is used to right-aligns the characters in String by padding them.

Step 1: Get the Number N and number of leading zeros P.

Step 2: Convert the number to string using the ToString() method.

val = N.ToString();

Step 3: Then pad the string by using the PadLeft() method.

pad_str = val.PadLeft(P, '0');

Step 4: Return the padded string.

Example :

C#

// C# program to pad an integer
// number with leading zeros
using System;

public class GFG{

    // Function to pad an integer number
    // with leading zeros
    static string pad_an_int(int N, int P)
    {
        // use of ToString() method
        string value = N.ToString();

        // use of the PadLeft() method
        string pad_str = value.PadLeft(P, '0');

        // return output
        return pad_str;
    }

    // driver code
    public static void Main(string[] args)
    {
        int N = 123; // Number to be pad
        int P = 5; // Number of leading zeros

        Console.WriteLine("Before Padding: " + N);

        // Function calling
        Console.WriteLine("After Padding: " + pad_an_int(N, P));
    }
}

Output:

Before Padding: 123
After Padding: 00123