restricting user input in csharp

To restrict user input in C#, you need to validate it before processing it further. Here are some techniques to achieve this:

1. Input validation: This is the process of checking user input to ensure that it meets the required format or structure. For example, if you're expecting an integer input, you can check if the user entered a valid integer or not.

main.cs
int number;
if (int.TryParse(input, out number))
{
    // input is a valid integer
}
else
{
    // input is not a valid integer
}
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2. Regular expressions: Regular expressions are a powerful way to validate user input by matching it against a predefined pattern. For example, if you're expecting a valid email address, you can use a regular expression to check if the input matches the expected pattern.

main.cs
Regex emailRegex = new Regex(@"^\w+@[a-zA-Z_]+?\.[a-zA-Z]{2,3}$");
if (emailRegex.IsMatch(input))
{
    // input is a valid email address
}
else
{
    // input is not a valid email address
}
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3. Try-catch: You can also use try-catch blocks to handle exceptions that might occur due to invalid user input. For example, if you're expecting a number but the user enters a string, you can handle the exception and display an error message to the user.

main.cs
try
{
    int number = Convert.ToInt32(input);
    // process the input further
}
catch (FormatException)
{
    // input is not a valid number
    Console.WriteLine("Invalid input. Please enter a number.");
}
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In summary, input validation is an important aspect of developing robust applications. By implementing techniques such as input validation, regular expressions, and try-catch blocks, you can ensure that your application handles user input correctly and gracefully handles any errors that might occur.