C# | BitConverter.ToInt32() Method

BitConverter.ToInt32(Byte[], Int32) Method is used to return a 32-bit signed integer converted from four bytes at a specified position in a byte array.
Syntax:

public static int ToInt32 (byte[] value, int startIndex);

Parameters:

value: It is an array of bytes. 
startIndex: It is the starting position within the value. 

Return Value: This method returns a 32-bit signed integer formed by two bytes beginning at startIndex.
Exceptions:

• ArgumentException: If the startIndex is greater than or equal to the length of value minus 3, and is less than or equal to the length of value minus 1.
• ArgumentNullException: If the value is null.
• ArgumentOutOfRangeException: If the startIndex is less than zero or greater than the length of value minus 1.

Below programs illustrate the use of BitConverter.ToInt32(Byte[], Int32) Method:
Example 1:

CSHARP

// C# program to demonstrate
// BitConverter.ToInt32(Byte[], Int32);
// Method
using System;

class GFG {

// Main Method
public static void Main()
{

    try {

        // Define an array
        // of byte values.
        byte[] bytes = {32, 0, 0, 42, 0,
                        65, 0, 125, 0, 197,
                        0, 168, 3, 41, 4,
                               125, 32 };

        // Display the values of the myArr.
        Console.Write("Initial Array: ");

        // calling the PrintIndexAndValues()
        // method to print
        PrintIndexAndValues(bytes);

        // print char value
        Console.WriteLine("index     byte Array           int value");
        for (int index = 0; index < bytes.Length - 3;
                              index = index + 4) {

            int values = BitConverter.ToInt16(bytes, index);

            Console.WriteLine(" {0}     {1}         {2}",
             index, BitConverter.ToString(bytes, index,
                                           4), values);
        }
    }
    catch (ArgumentNullException e) {

        Console.Write("Exception Thrown: ");
        Console.Write("{0}", e.GetType(), e.Message);
    }
    catch (ArgumentOutOfRangeException e) {

        Console.Write("Exception Thrown: ");
        Console.Write("{0}", e.GetType(), e.Message);
    }
    catch (ArgumentException e) {

        Console.Write("Exception Thrown: ");
        Console.Write("{0}", e.GetType(), e.Message);
    }
}

// Defining the method
// PrintIndexAndValues
public static void PrintIndexAndValues(byte[] myArr)
{
    for (int i = 0; i < myArr.Length; i++) {

        Console.Write("{0} ", myArr[i]);
    }

    Console.WriteLine();
    Console.WriteLine();
}
}

Output:

Initial Array: 32 0 0 42 0 65 0 125 0 197 0 168 3 41 4 125 32 

index      byte Array       int value
  0        20-00-00-2A         32
  4        00-41-00-7D         16640
  8        00-C5-00-A8         -15104
  12        03-29-04-7D         10499

Example 2: For ArgumentException

CSHARP

// C# program to demonstrate
// BitConverter.ToInt32(Byte[], Int32);
// Method
using System;

class GFG {

// Main Method
public static void Main()
{

    try {

        // Define an array
        // of byte values.
        byte[] bytes = {32, 0, 0, 42, 0,
                        65, 0, 125, 0, 197,
                        0, 168, 3, 41, 4, 125};

        // Display the values of the myArr.
        Console.Write("Initial Array: ");

        // calling the PrintIndexAndValues()
        // method to print
        PrintIndexAndValues(bytes);

        // print char value
        Console.WriteLine("index      element          int value");
        for (int index = 1; index < bytes.Length - 2;
                                 index = index + 4) {

            if (index == bytes.Length - 3) {
                Console.WriteLine();
                Console.WriteLine("startIndex equals the "+
                               "length of value minus 3.");
                int values = BitConverter.ToInt32(bytes, index);
                Console.WriteLine("  {0}      {1}         {2}",
                 index, BitConverter.ToString(bytes, index, 4), values);
            }
            else {
                int values = BitConverter.ToInt32(bytes, index);
                Console.WriteLine("  {0}      {1}         {2}",
                 index, BitConverter.ToString(bytes, index, 4), values);
            }
        }
    }
    catch (ArgumentNullException e) {

        Console.Write("Exception Thrown: ");
        Console.Write("{0}", e.GetType(), e.Message);
    }
    catch (ArgumentOutOfRangeException e) {

        Console.Write("Exception Thrown: ");
        Console.Write("{0}", e.GetType(), e.Message);
    }
    catch (ArgumentException e) {

        Console.Write("Exception Thrown: ");
        Console.Write("{0}", e.GetType(), e.Message);
    }
}

// Defining the method
// PrintIndexAndValues
public static void PrintIndexAndValues(byte[] myArr)
{
    for (int i = 0; i < myArr.Length; i++) {

        Console.Write("{0} ", myArr[i]);
    }

    Console.WriteLine();
    Console.WriteLine();
    Console.WriteLine("initial Array in string: {0} ",
                       BitConverter.ToString(myArr));
    Console.WriteLine();
}
}

Output:

Initial Array: 32 0 0 42 0 65 0 125 0 197 0 168 3 41 4 125 

initial Array in string: 20-00-00-2A-00-41-00-7D-00-C5-00-A8-03-29-04-7D 

index      element          int value
  1      00-00-2A-00         2752512
  5      41-00-7D-00         8192065
  9      C5-00-A8-03         61341893

startIndex equals the length of value minus 3.
Exception Thrown: System.ArgumentException

Example 3: For ArgumentOutOfRangeException

CSHARP

// C# program to demonstrate
// BitConverter.ToInt32(Byte[], Int32);
// Method
using System;

class GFG {

// Main Method
public static void Main()
{

    try {

        // Define an array
        // of byte values.
        byte[] bytes = {32, 0, 0, 42, 0, 65,
                        0, 125, 0, 197, 0,
                        168, 3, 41, 4, 125};

        // Display the values of the myArr.
        Console.Write("Initial Array: ");

        // calling the PrintIndexAndValues()
        // method to print
        PrintIndexAndValues(bytes);

        // print char value
        Console.WriteLine("index      element          int value");

        for (int index = 0; index < bytes.Length + 1;
                                index = index + 4) {

            if (index == bytes.Length) {
                Console.WriteLine();
                Console.WriteLine("startIndex is greater than "+
                                 "the length of value minus 1");
                int values = BitConverter.ToInt32(bytes, index);
                Console.WriteLine("  {0}      {1}         {2}",
                 index, BitConverter.ToString(bytes, index, 4), values);
            }
            else {
                int values = BitConverter.ToInt32(bytes, index);
                Console.WriteLine("  {0}      {1}         {2}",
                 index, BitConverter.ToString(bytes, index, 4), values);
            }
        }
    }
    catch (ArgumentNullException e) {

        Console.Write("Exception Thrown: ");
        Console.Write("{0}", e.GetType(), e.Message);
    }
    catch (ArgumentOutOfRangeException e) {

        Console.Write("Exception Thrown: ");
        Console.Write("{0}", e.GetType(), e.Message);
    }
    catch (ArgumentException e) {

        Console.Write("Exception Thrown: ");
        Console.Write("{0}", e.GetType(), e.Message);
    }
}

// Defining the method
// PrintIndexAndValues
public static void PrintIndexAndValues(byte[] myArr)
{
    for (int i = 0; i < myArr.Length; i++) {

        Console.Write("{0} ", myArr[i]);
    }

    Console.WriteLine();
    Console.WriteLine();
    Console.WriteLine("initial Array in string: {0} ",
                       BitConverter.ToString(myArr));
    Console.WriteLine();
}
}

Output:

Initial Array: 32 0 0 42 0 65 0 125 0 197 0 168 3 41 4 125 

initial Array in string: 20-00-00-2A-00-41-00-7D-00-C5-00-A8-03-29-04-7D 

index      element          int value
  0      20-00-00-2A         704643104
  4      00-41-00-7D         2097168640
  8      00-C5-00-A8         -1476344576
  12      03-29-04-7D         2097424643

startIndex is greater than the length of value minus 1
Exception Thrown: System.ArgumentOutOfRangeException

Example 4: For ArgumentNullException

CSHARP

// C# program to demonstrate
// BitConverter.ToInt32(Byte[], Int32);
// Method
using System;

class GFG {

// Main Method
public static void Main()
{

    try {

        // Define an array of byte values.
        byte[] bytes = null;

        // get the int value

        int values = BitConverter.ToInt32(bytes, 0);
        Console.Write("{0}", values);
    }
    catch (ArgumentNullException e) {

        Console.Write("Exception Thrown: ");
        Console.Write("{0}", e.GetType(), e.Message);
    }
    catch (ArgumentOutOfRangeException e) {

        Console.Write("Exception Thrown: ");
        Console.Write("{0}", e.GetType(), e.Message);
    }
    catch (ArgumentException e) {

        Console.Write("Exception Thrown: ");
        Console.Write("{0}", e.GetType(), e.Message);
    }
}
}

Output:

Exception Thrown: System.ArgumentNullException

Reference:

• https://docs.microsoft.com/en-us/dotnet/api/system.bitconverter.toint32?view=netframework-4.7.2