如何在c#中使用mysql验证数据库中已有的用户名

string connectionString = "server=数据库服务器地址;user=用户名;password=密码;database=数据库名称;";
MySqlConnection connection = new MySqlConnection(connectionString);
connection.Open();

string username = "要验证的用户名";
string query = "SELECT COUNT(*) FROM 用户表名 WHERE 用户名 = @username";
MySqlCommand command = new MySqlCommand(query, connection);
command.Parameters.AddWithValue("@username", username);

int count = Convert.ToInt32(command.ExecuteScalar());

if (count > 0)
{
    Console.WriteLine("用户名已存在");
}
else
{
    Console.WriteLine("用户名可用");
}

connection.Close();