Convert List Of Object To Array

I am working where I need to create question randomly to use it later to create question paper, so what I have do is creating class Gene which represent question then create a list

Solution 1:

a field initializer cannot reference the nonstatic field method or property

The issue is that you have a field initializer referencing a non-static field, method or property. The C# compiler won't allow that.

One solution is to move from a field to a property:

Gene[] s { get { return QestionList.ToArray(); } }

The downside of above is that whenever you access s you are effectively cloning QestionList (i.e. it is expensive).

Another would be to leave your field there:

Gene[] s;

and populate it inside your constructor instead:

s = QestionList.ToArray();

The upside of doing it in the constructor is that the cloning will occur only once. That is also the downside (if you are altering QestionList then s won't reflect that).

Solution 2:

This should work :). I think that you are using it in wrong place. Please show a code where are you converting list to array.

strings="select * Question, CLO, Question_Type FROM QuestionBank WHERE (Subject = '" + sub + "') AND (chapter = '" + chapter + "') AND (Question_Type = '" + qt.name + "') ORDER BY RAND() LIMIT = '" + qt.numOfType;
                SqlCommandcmd=newSqlCommand(s, con);
                SqlDataReader dr;
                con.Open();
                dr = cmd.ExecuteReader();
                dr.Read();
                while (dr.Read())
                {
                    stringques= dr["Question"].ToString();
                    stringquestype= dr["Question_Type"].ToString();
                    stringquesCLO= dr["CLO"].ToString(); 
                    QuestionList.Add(newGene (ques, questype, quesCLO));
                }
                 con.Close();
                 vargeneArray= QuestionList.ToArray()
               }

Solution 3:

Lists can trivially be converted to arrays via ToArray(). The real problem here is simply: timing and location. The code that calls ToArray() is fine in a method, for example it would be fine at the bottom of a method like:

Gene[] GetThings(string subject, string chapter, ...)
{
   var list = new List<Gene>();
   ... some code that populates list

   return list.ToArray();
}

Likewise, at the end of that method you could assign to a property or field:

SomeMember = list.ToArray();