Ошибка подключения к базе данных

 private string BuildConnectionString(string _Server, string _Database, string _Username, string _Password) 
{ 
    string Result = $"Server={_Server}; Database={_Database}"; 
    if (_Username != string.Empty) 
        Result += $"; User ID={_Username}; Password={_Password}"; 
    else 
        Result += "; Integrated Security='true'"; 
    return Result; 
} 
 
public SqlConnection Connect(string _Server, string _Database, string _Username, string _Password) 
{     
    string ConnStr = BuildConnectionString(_Server, _Database, _Username, _Password); 
    SqlConnection Conn = new SqlConnection(ConnStr); 
    Conn.Open(); 
    return Conn;
}