There are many common mistakes made during .NET (ASP.NET, .NET Core) development, which affect performance, security, and code maintainability. Let's learn about 7 common mistakes and their solutions.

1. Not closing the database connection properly

Many developers forget to close the database connection ('SqlConnection') after opening it. This results in memory leaks and increases the server load.

Solution -

using (SqlConnection conn = new SqlConnection(connectionString))
{
    conn.Open();
    // Database operations
}

2. Using hardcoded strings

Many people write application configuration or sensitive information directly into the code, which is a security risk.

Solution:

  • Use appsettings.json or Environment Variables.
using (SqlConnection conn = new SqlConnection(connectionString))
{
    conn.Open();
    // Database operations
}

3. Not handling exceptions

Without proper exception handling, the application can crash unexpectedly.

Solution:

try
{
    int result = 10 / int.Parse("0"); // Division by zero
}
catch (Exception ex)
{
    Console.WriteLine($"Error: {ex.Message}");
}

4. Not preventing SQL injection

Many people use user input directly in SQL statements, which opens up opportunities for SQL injection attacks.

Solution:

using (SqlCommand cmd = new SqlCommand("SELECT * FROM Users WHERE UserId = @id", conn))
{
    cmd.Parameters.AddWithValue("@id", userId);
}

5. Not logging and monitoring

Without logging, it becomes difficult to find application problems.

Solution:

  • Use Serilog, NLog, or Application Insights.
Log.Information("User logged in: {UserId}", userId);

6. Using unnecessary viewstate and large sessions

Using large viewstate in ASP.NET WebForms slows down the webpage. Similarly, large session data increases the memory usage of the server.

Solution:

  • Minimize or disable ViewState.
  • Reduce Session Timeout.

7. Not using asynchronous programming

If asynchronous methods are not used while a heavy operation is running, the application may block.

Solution:

public async Task<string> GetDataAsync()
{
    using (HttpClient client = new HttpClient())
    {
        return await client.GetStringAsync("https://api.example.com/data");
    }
}

Avoiding these 7 common mistakes will make your .NET application more secure, performant, and resource-efficient. If you have any experiences or feedback, please share them in the comments!