How to Put Special Characters in a MySQL Password in a .NET C# Connection String

A connection string is a list of name=value pairs, split by ;. So a ; in your password ends the value early, and the rest looks like a strange option. Here's every case I tested, and the way to avoid thinking about it.

The Rules

Password	Write it as	Result
a=b	Password=a=b	Connects: no quotes needed
a b	Password=a b	Connects: a space in the middle is fine
abc;def	Password='abc;def' or Password="abc;def"	Connects
abc;def	Password=abc;def	Option not supported
A space at each end	Password=' ab '	Connects. With no quotes, the spaces are dropped, and you get Access denied
a'b	Password="a'b" or Password='a''b'	Connects: double a ' inside single quotes
a"b	Password='a"b' or Password="a""b"	Connects: double a " inside double quotes

So the simple habit is single quotes around the password, with any ' inside it doubled.

See the Failure

With the password abc;def and no quotes:

Output

Unhandled exception. System.ArgumentException: Option not supported (Parameter 'def;sslmode')

Notice what's in that message: def is the end of the password. In an app, that exception lands in your log. If that's happened, treat the password as exposed.

Fix It with Quotes

Connection string

Server=127.0.0.1;Port=3306;Database=inventory;User ID=quote_demo;Password='abc;def';SslMode=Required

Output

Connected as quote_demo@% to MySQL 9.7.4
TLS: TLSv1.2

And a password with both an apostrophe and a semicolon, it's;ok, doubled:

Connection string

…;Password='it''s;ok';SslMode=Required

Output

Connected as quote_demo@% to MySQL 9.7.4
TLS: TLSv1.2

These quotes are part of the connection string, and are separate from whatever your shell does. To set it from a terminal, put the whole string in double quotes, and those single quotes inside it.

Or Let the Driver Do It

If you build the string in code, MySqlConnectionStringBuilder handles every case. This one has ', " and ; together:

connection-string.cs

// 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);

Output

server=127.0.0.1;port=3306;database=inventory;user id=inventory_app;password="a'b""c;d";sslmode=Required

Or Avoid the Problem

A hex password has no special characters at all, and it's just as strong:

macOS / Linux

Terminal

openssl rand -hex 24

Windows (PowerShell)

PowerShell

$bytes = [byte[]]::new(24); [System.Security.Cryptography.RandomNumberGenerator]::Create().GetBytes($bytes); -join ($bytes | ForEach-Object { $_.ToString('x2') })

How to Generate a Strong Random Password in the Terminal explains it. MySQL's own IDENTIFIED BY RANDOM PASSWORD is the opposite: it can produce all of these characters.

Common Mistakes

Mistake	What happens	Do this instead
Escaping with a backslash	The ; still ends the value	Quote the value
Quoting only in the shell	The shell removes those quotes	Quote inside the string
Building the string with $"…Password={password}…"	It breaks on the first odd password	Use the builder

Troubleshooting

Symptom	Likely cause	Fix
Option not supported (Parameter …)	An unquoted ;	The fix
Incorrect value in Connection String near 'Password'	An opening quote with no closing quote	Check the quotes match
Access denied	A character changed on its way through a shell, or spaces at the ends	The fix

Conclusion

Put the password in single quotes, and double any ' inside. Or use MySqlConnectionStringBuilder, or generate hex passwords and skip the problem.

Additional Resources

• Creating a Connector/NET Connection String — the format.
• Connector/NET Connection Options — every option.

Related

• How to Read and Build a Connection String with MySqlConnectionStringBuilder
• How to Write a MySQL Connection String for .NET C#
• How to Generate a Strong Random Password in the Terminal