How To Convert String To Integer In C#

In the Present time period Converting a string to an integer is a common task in programming, and C# offers several built-in methods for performing this operation. This conversion is often necessary when processing user input or performing computations on strings.

In this blog, we will discuss different approaches and sample problems as well to help you practice and gain a better understanding of how to convert string data to integer in C#.

So, let’s start the journey and gain some knowledge of converting a string to an integer in C#.

Why is converting string to integer in C# is needed?

Converting strings to integers in C# is necessary for several reasons, including:

• User Input: When accepting input from users, it is typically received as a string. Converting these string inputs to integers allows for mathematical calculations and comparisons to be performed accurately.
• Database Operations: Many databases store numeric data as strings, especially when dealing with data from external sources.
• Interoperability: When integrating with external systems or APIs that exchange data in string format, it may be necessary to convert these strings to integers for compatibility with the internal data types of the C# application.

How To Convert String To Integer In C#

Here are five different approaches to how to convert string to integer in C# with detailed solution steps, code, and output for each approach:

1. Using Convert.ChangeType()
2. Using a custom parsing method
3. Using Convert.ToInt32()
4. Using int.Parse()
5. Using int.Parse() with NumberStyles

Let’s dive in more with examples to each approach.

Approach 1: Using Convert.ChangeType()

The dynamic runtime conversion of various data types, specifically integers, can be achieved through the utilization of the Convert.ChangeType() method.

Pros:

1. Supports conversion to various data types, not limited to integers.
2. Provides flexibility for handling different data types during runtime.
3. Allows for custom type converters to be used.

Cons:

1. May throw an exception if the string cannot be converted to the desired data type.
2. Requires explicit casting to the desired data type after conversion.
3. Slower compared to other methods due to dynamic runtime conversion.

Code:

using System;

public class Program
{
    public static void Main()
    {
        string str = "7457";
        object obj = Convert.ChangeType(str, typeof(int)); // Convert string to object using ChangeType()
        int num = (int)obj; // Cast the object to int
        Console.WriteLine(num);
    }
}

Output:

7457

Code Explanation:

1. Convert.ChangeType() method is used to convert the string to an object, allowing for runtime conversion to different data types.
2. The desired data type (in this case, int) is specified as the second parameter of ChangeType().
3. The object is then cast to int to obtain the integer value.

Approach 2: Using a custom parsing method

This approach involves implementing a custom parsing method that parses the string and converts it to an integer using custom logic.

Pros:

1. Allows for customization of parsing logic according to specific requirements.
2. Provides flexibility in handling different formats or styles of input strings.
3. Can handle cases where other built-in methods may not be suitable.

Cons:

1. Requires additional implementation effort to create and maintain a custom parsing method.
2. May not be as efficient as built-in methods for simple string-to-integer conversions.
3. May require additional error handling to handle different scenarios.

Code:

using System;

class Program
{
    static int MyCustomParseInt(string str)
    {
        int result = 0;
        int sign = 1;
        int i = 0;

        if (str[0] == '-')
        {
            sign = -1;
            i = 1;
        }

        for (; i < str.Length; i++)
        {
            if (char.IsDigit(str[i]))
            {
                result = result * 10 + (str[i] - '0');
            }
            else
            {
                throw new ArgumentException("Invalid input: " + str);
            }
        }

        return result * sign;
    }

    static void Main(string[] args)
    {
        string str = "123";
        int num = MyCustomParseInt(str); // Call custom parsing method
        Console.WriteLine("Parsed integer: " + num);
    }
}

Output:

Parsed integer: 123

Code Explanation:

1. A custom parsing method (MyCustomParseInt() in this case) is implemented to handle the string-to-integer conversion with custom logic.
2. The custom method can be implemented using techniques such as regular expressions, string manipulation, or any other custom parsing logic.
3. The parsed integer value is returned from the custom method.

Approach 3: Using Convert.ToInt32()

The current writing suggests utilization of the Convert.ToInt32() approach, which is a built-in, natively-supported method in C#, that serves the explicit purpose of converting a string of characters into an integer.

Pros:

1. Simple and easy-to-use method for converting strings to integers.
2. Provides built-in error handling for invalid input strings.
3. Automatically handles culture-specific formatting of input strings.

Cons:

1. May throw an exception if the string cannot be converted to an integer.
2. Limited customization options for parsing logic or formatting.
3. Slower compared to int.Parse() for simple string-to-integer conversions.

Code:

using System;

class Program
{
    static void Main()
    {
        string str = "90456";
        int num;

        if (Int32.TryParse(str, out num))
        {
            // Convert string to int using TryParse()
            Console.WriteLine("Successfully converted string to int: " + num);
        }
        else
        {
            Console.WriteLine("Failed to convert string to int.");
        }
    }
}

Output:

Successfully converted string to int: 90456

Code Explanation:

1. The Convert.ToInt32() method is used to directly convert the string to an integer.
2. The input string is automatically parsed using the current culture settings, which may affect the parsing of the string based on the culture-specific formatting of numbers.

Approach 4: Using int.Parse()

The utilization of the int.Parse() method is a prominent approach that leverages the built-in capabilities of the C# programming language to enable direct conversion of a string datatype to its integer

Pros:

1. Simple and easy-to-use method for converting strings to integers.
2. Provides built-in error handling for invalid input strings.
3. Faster compared to Convert.ToInt32() for simple string-to-integer conversions.

Cons:

1. May throw an exception if the string cannot be converted to an integer.
2. Limited customization options for parsing logic or formatting.
3. Does not handle culture-specific formatting of input strings.

Code:

using System;

public class Program
{
    public static void Main()
    {
        string str = "67453";
        int num = Convert.ToInt32(str); // Convert string to int using Convert.ToInt32()
        Console.WriteLine("num = " + num); // Output the converted integer
    }
}

Output:

num = 67453

Code Explanation:

1. The int.Parse() method is used to directly convert the string to an integer.
2. It is faster compared to Convert.ToInt32() as it does not handle culture-specific formatting.
3. However, it may throw an exception if the string cannot be converted to an integer.

Approach 5: Using int.Parse() with NumberStyles

This approach uses the int.Parse() method with NumberStyles enumeration to specify additional options for parsing the input string, such as allowing leading/trailing white spaces, specifying culture-specific formatting, etc.

Pros:

1. Provides additional options for customization of parsing logic and formatting.
2. Supports culture-specific formatting of input strings.
3. Faster compared to Convert.ToInt32() for simple string-to-integer conversions.

Cons:

1. May throw an exception if the string cannot be converted to an integer.
2. Requires additional understanding of NumberStyles enumeration and its options.
3. Limited error handling for specific scenarios.

Code:

using System;
using System.Globalization;

class Program
{
    static void Main()
    {
        string str = "46,224";
        int num = ParseIntWithThousands(str);
        Console.WriteLine("Parsed Int: " + num);
    }

    static int ParseIntWithThousands(string str)
    {
        int num = 0;
        bool negative = false;

        // Check if the string starts with a minus sign
        if (str.StartsWith("-"))
        {
            negative = true;
            str = str.Substring(1); // Remove the minus sign
        }

        // Remove thousands separator from the string
        str = str.Replace(",", "");

        // Parse the string to int
        if (int.TryParse(str, NumberStyles.AllowLeadingSign, CultureInfo.InvariantCulture, out num))
        {
            if (negative)
            {
                num *= -1; // Apply negative sign if necessary
            }
            return num;
        }
        else
        {
            Console.WriteLine("Failed to parse string to int.");
            return 0; // Return default value or handle error case as needed
        }
    }
}

Output:

Parsed Int: 46224

Code Explanation:

1. The int.Parse() method is used with additional parameters NumberStyles and CultureInfo to specify parsing options and culture-specific formatting.
2. In this example, NumberStyles.AllowThousands and NumberStyles.AllowLeadingSign options are used to allow thousands separators and leading signs in the input string.
3. CultureInfo.InvariantCulture is used to specify the culture-independent formatting of numbers.

Best Approach To Convert String To Integer In C#

The best qualities of using the Convert.ChangeType()  approach for converting a string to integer in C# are:

• Flexibility: Convert.ChangeType() allows for dynamic runtime conversion to different data types, providing flexibility for handling various data types during runtime.

• Customization: This approach supports custom type converters to be used, allowing for customized conversion logic to be implemented as needed.

• Support for various data types: Convert.ChangeType() supports conversion to various data types, not limited to integers, making it a versatile conversion method.

Sample Problems To Convert String To Integer In C#

Sample Problem 1:

Scenario: A data analyst has a dataset containing numerical values stored as strings, and they need to convert those strings to integers for data analysis.

Solution Steps:

1. Declare a string variable and assign the value “1234” to it.
2. Use Convert.ChangeType() to convert the string to an integer.
3. Print the integer value.

Code:

using System;

public class Program {
    public static void Main() {
        string numString = "1234";
        if (int.TryParse(numString, out int numInt)) {
            Console.WriteLine(numInt);
        } else {
            Console.WriteLine("Failed to convert string to integer.");
        }
    }
}

Output:

1234

Sample Problem 2:

Scenario: A doctor has a patient database where patient ages are stored as strings, and they need to convert those strings to integers for analysis.

Solution Steps:

1. Declare a string variable and assign the value “35” to it.
2. Create a custom parsing method that uses the int.TryParse() method to convert the string to an integer.
3. Call the custom parsing method with the string variable as an argument.
4. Print the integer value.

Code:

using System;

public class Program {
    public static void Main() {
        string ageString = "35"; // declare and initialize the string variable
        int ageInt = CustomParse(ageString); // call the custom parsing method with the string variable
        Console.WriteLine(ageInt); // print the integer value
    }
    
    // custom parsing method
    public static int CustomParse(string str) {
        int num;
        if (int.TryParse(str, out num)) {
            return num;
        } else {
            throw new Exception("Invalid input string.");
        }
    }
}

Output:

35

Sample Problem 3:

Scenario: A cycle manufacturer has a product database where the number of wheels on each cycle is stored as strings, and they need to convert those strings to integers for analysis.

Sample Problem: Convert the string “2” to an integer using Convert.ToInt32().

Solution Steps:

1. Declare a string variable and assign the value “2” to it.
2. Use Convert.ToInt32() to convert the string to an integer.
3. Print the integer value.

Code:

using System;

public class Program {
    public static void Main() {
        string wheelsString = "2"; // declare and initialize the string variable
        int wheelsInt = Int32.Parse(wheelsString); // convert the string to integer using Parse()
        Console.WriteLine(wheelsInt); // print the integer value
    }
}

Output:

2

Sample Problem 4:

Scenario: A music teacher has a student database where student ages are stored as strings, and they need to convert those strings to integers for analysis.

Solution Steps:

1. Declare a string variable and assign the value “10” to it.
2. Use int.Parse() to convert the string to an integer.
3. Print the integer value.

Code:

using System;

public class Program {
    public static void Main() {
        string ageString = "10"; // declare and initialize the string variable
        int ageInt = Convert.ToInt32(ageString); // convert the string to integer using Convert.ToInt32()
        Console.WriteLine(ageInt); // print the integer value
    }
}

Output:

10

Sample Problem 5:

Scenario: A watch manufacturer has a database where the prices of different watches are stored as strings with a currency symbol, and they need to convert those strings to integers for analysis.

Solution Steps:

1. Declare a string variable and assign the value “$200” to it.
2. Create a NumberStyles object that includes the Currency flag.
3. Use int.Parse() with the NumberStyles object to convert the string to an integer.
4. Print the integer value.

Code:

using System;
using System.Globalization;

public class Program {
    public static void Main() {
        string priceString = "$200"; // declare and initialize the string variable
        NumberStyles style = NumberStyles.Currency; // create a NumberStyles object with Currency flag
        int priceInt = int.Parse(priceString.Replace("$", ""), style); // convert the string to integer using Parse() with NumberStyles
        Console.WriteLine(priceInt); // print the integer value
    }
}

Output:

200

Conclusion

In conclusion, converting a string to an integer in C# is a common task that can be accomplished by using different approaches. The best approach comes up is Convert.ChangeType().It is flexible, customized and widely supported.We have explored other approaches as well in this blog. Those are also good. By choosing the appropriate approach, you can ensure accurate and efficient conversion of strings to integers in your C# application.