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

26 May, 2020
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 zerosusing 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 zerosusing 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 zerosusing 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

C#
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