How to Compare Two Textbox Values in ASP.NET C#

Comparing textbox values for user authentication is a common task in web development. This article provides a guide on how to effectively compare two textbox values in ASP.NET C# for scenarios like login forms. We’ll explore techniques for reading, comparing, and validating user input against stored credentials.

Reading and Comparing Textbox Values

In ASP.NET C#, textbox values are accessed through their Text property. To compare two textboxes, retrieve the values from each textbox and use the Equals method for a case-sensitive comparison or string.Compare for case-insensitive comparison. For security reasons, it’s generally recommended to perform a case-sensitive comparison for passwords.

string username = TextBox1.Text;
string password = TextBox2.Text;

if (username.Equals("storedUsername") && password.Equals("storedPassword"))
{
  // Successful login
}
else
{
  // Invalid credentials
}

Validating Against Stored Credentials

Typically, user credentials are stored securely in a database. For this example, let’s assume credentials are stored in a text file with each line representing a username and password pair separated by a comma (e.g., “username,password”).

To validate user input:

1. Read the text file: Use System.IO.File.ReadAllLines to read all lines from the file.
2. Parse each line: Split each line into username and password using string.Split(',').
3. Compare with input: Compare the extracted username and password with the textbox values using the comparison methods mentioned earlier.

string[] lines = System.IO.File.ReadAllLines("users.txt");

foreach (string line in lines)
{
  string[] credentials = line.Split(',');
  if (credentials.Length == 2 && username.Equals(credentials[0]) && password.Equals(credentials[1]))
  {
      // Successful login
      break;
  }
}

Security Considerations

• Hashing Passwords: Never store passwords in plain text. Always hash passwords using a strong one-way hashing algorithm (e.g., bcrypt, PBKDF2) before storing them. Compare the hash of the entered password with the stored hash.
• Salting: Use a unique salt for each password to further protect against rainbow table attacks.
• Input Sanitization: Sanitize user input to prevent injection attacks (e.g., SQL injection, cross-site scripting).

Conclusion

Comparing textbox values in ASP.NET C