How to Read and Build a Connection String with MySqlConnectionStringBuilder

MySqlConnectionStringBuilder turns a MySQL connection string into named properties, in both directions. It writes a valid string whatever your password holds, and it reads one back, with every default filled in. That's handy for logging settings without the password.

What You Need

The .NET 10 SDK. This is a one-file program, as in How to Run a Single C# File with dotnet run. In an app that uses Oracle's EF Core provider, MySql.Data is already there.

The Program

Save this as connection-string.cs:

connection-string.cs

#:package MySql.Data@26.10.0

using MySql.Data.MySqlClient;

// The builder quotes every value for you, whatever characters it holds.
var builder = new MySqlConnectionStringBuilder
{
    Server = "127.0.0.1",
    Port = 3306,
    Database = "inventory",
    UserID = "inventory_app",
    Password = "a'b\"c;d",
    SslMode = MySqlSslMode.Required,
};

Console.WriteLine(builder.ConnectionString);

// And it reads a string back into named properties.
var settings = new MySqlConnectionStringBuilder("Server=db.example.com;Database=inventory;User ID=app;Password=x;Maximum Pool Size=25");
Console.WriteLine($"Server: {settings.Server}");
Console.WriteLine($"Port: {settings.Port}");
Console.WriteLine($"SslMode: {settings.SslMode}");
Console.WriteLine($"MaximumPoolSize: {settings.MaximumPoolSize}");
Console.WriteLine($"ConnectionTimeout: {settings.ConnectionTimeout}");
Console.WriteLine($"ConnectionLifeTime: {settings.ConnectionLifeTime}");
Console.WriteLine($"MinimumPoolSize: {settings.MinimumPoolSize}");
Console.WriteLine($"PersistSecurityInfo: {settings.PersistSecurityInfo}");

Terminal

dotnet run connection-string.cs

Output

server=127.0.0.1;port=3306;database=inventory;user id=inventory_app;password="a'b""c;d";sslmode=Required
Server: db.example.com
Port: 3306
SslMode: Preferred
MaximumPoolSize: 25
ConnectionTimeout: 15
ConnectionLifeTime: 0
MinimumPoolSize: 0
PersistSecurityInfo: False

Building

The first line of output is the string it wrote. The password a'b"c;d has all the awkward characters, and the builder quoted it correctly: password="a'b""c;d".

So if your app puts a connection string together from separate settings, use this. Don't build it with string interpolation, which breaks on the first unusual password.

Reading

The rest of the output comes from a string that only set a few things. Everything else came back as its default, so this also answers "what does this string really use?":

Property	Value	Note
Port	3306	Not in the string
SslMode	Preferred	Not in the string, and it falls back to no encryption
MaximumPoolSize	25	In the string
ConnectionTimeout	15	The default, in seconds

An app can use these properties too. For example, this reads the pool size to size a limit on requests:

Program.cs

var maximumPoolSize = (int)new MySqlConnectionStringBuilder(connectionString).MaximumPoolSize;

How to Limit Concurrent Requests in ASP.NET Core explains why you'd want that.

Logging Settings Safely

Read the settings you want by name, and you can't log the password by accident. How to Log the Database Settings When an ASP.NET Core App Starts shows this. Don't log .ConnectionString, because it includes the password.

Common Mistakes

Mistake	What happens	Do this instead
Logging builder.ConnectionString	The password's in your log	Log named settings
Assuming an unset SslMode means encrypted	It's Preferred	Set it
Passing a string with an unquoted ; in the password	The constructor throws, with part of the password in its message	Quote it

Troubleshooting

Symptom	Likely cause	Fix
Option not supported (Parameter …)	An unknown name, or a ; in a value	The fix
CS0246 for MySqlConnectionStringBuilder	The using is missing	Add using MySql.Data.MySqlClient;
CS0266 on MaximumPoolSize	It's a uint	Cast it: (int)

Conclusion

Use MySqlConnectionStringBuilder to write connection strings that can't break, and to read one to see what it really means.

Additional Resources

• Connector/NET API reference — the MySqlConnectionStringBuilder class.
• Connector/NET Connection Options — what they mean.

Related

• How to Write a MySQL Connection String for .NET C#
• How to Put Special Characters in a MySQL Password in a .NET C# Connection String
• How to Log the Database Settings When an ASP.NET Core App Starts