Stuck on SqlDataReader.GetValues Method

Question 1

The error you encounter is located in this line:

myObject = reader.GetValues(myObject);

myObject is an array of objects and the GetValues method returns an integer that contains the count that is placed in the array. So in order to solve your error, you can change the line to the following:

var count = reader.GetValues(myObject);

Also, in your code, you only retrieve one row of data. This is - of course - fine if you only expect one row. When expecting multiple rows, you typically loop over the rows like this:

while (reader.Read())
{
    // Read row and add row to list
}

For a sample on how to use SqlDataReader, see this link.

Sample

If you want to retrieve multiple rows and store the data, I suggest to add a class to store the data of a row (you might want to verify the data types so that they match the types that the SP returns):

public class Data
{
    public string DeptApp { get; set; }
    public string Status { get; set; } // this might be another data type
    public string Supervisor { get; set; }
}

Then retrieve the rows as follows:

public Data[] GetDeptAppData()
{
    //execute stored procedure to get data from database
    using (SqlConnection sqlConnection = new SqlConnection("Data Source=MyServer;Initial Catalog=MyCatalog;Persist Security Info=True;User ID=MyUser;Password=MyPassword"))
    {
        SqlCommand cmd = new SqlCommand();
        cmd.CommandText = "SP_Admin_DeptApp_Load";
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Connection = sqlConnection;
        sqlConnection.Open();
        using (var reader = cmd.ExecuteReader())
        {
            if (!reader.HasRows)
            {
                // throw exception
            }
            var lst = new List<Data>();
            while (reader.Read())
            {
                var row = new Data();
                row.DeptApp = reader.GetString(0);
                row.Status = reader.GetString(1);
                row.Supervisor = reader.GetString(2);
                lst.Add(row);
            }
            return lst.ToArray();
        }
    }
}

Question 2

GetValues returns an int which is "The number of instances of Object in the array.", so you cannot assign that to myObject. This is cryptic. It actually means (I believe) the number of column values returned for the current row.

You need:

int numColumnsRetrieved = reader.GetValues(myObject);

or something similar.

Your data is then present inside myObject, but only for the current row, as per the docs "Populates an array of objects with the column values of the current row". So, you still need to iterate, such as:

var myObjectList = new List<object[]>(); // ... shudder ...
while (reader.Read())
{
    var myObject[] = new object[reader.FieldCount];
    int instances = reader.GetValues(myObject);
    myObjectList.Add(myObject);
}

You might find it useful to use a method that is more specific, such as GetString:

var usersAndBosses = new List<Tuple<string, string>>();
while (reader.Read())
{
    string username = reader.GetString(0); // column index 0
    string bossname = reader.GetString(1); // column index 1
    usersAndBosses.Add(Tuple.Create(username, bossname));
}

EDIT

If you want a spurious use for the return value from GetValues, you could flatten a table of strings into a list of strings:

var myStringList = new List<string>();
while (reader.Read())
{
    var myObject[] = new object[100];
    int colCount = reader.GetValues(myObject);
    for (int i = 0; i < colCount; i++)
    {
        myStringList.Add((string)myObject[i]);
    }
}

Question 3

Below there is ExecuteSelectQuery(...) function to get resuls of any SELECT queries.

The result of ExecuteSelectQuery is a list of arrays of System.Object elements which can be transformed to required types in calling code.

public sealed class DbPerformer
{
    private const string mySqlServerName = "localhost";
    private const string dataBaseName = "testdb";
    private const string uid = "login";
    private const string password = "password";

    private MySqlConnection connection;

    public DbPerformer()
    {
        string connectionString;
        connectionString = "server=" + mySqlServerName + ";";
        connectionString += "Username=" + uid + ";";
        connectionString += "Password=" + password;

        connection = new MySqlConnection(connectionString);
    }

    private bool OpenConnection()
    {
        try
        {
            connection.Open();
            return true;
        }
        catch (MySqlException ex)
        {
            switch (ex.Number)
            {
                case 0:
                    Debug.WriteLine("Cannot connect to server {0}", mySqlServerName);
                    break;

                case 1045:
                    Debug.WriteLine("Invalid username/password.");
                    break;
            }
            return false;
        }
    }

    private bool CloseConnection()
    {
        try
        {
            connection.Close();
            return true;
        }
        catch (MySqlException ex)
        {
            Debug.WriteLine(ex.Message);
            return true;
        }
    }

    public List<object[]> ExecuteSelectQuery(string selectQuery)
    {
        List<object[]> resultList = new List<object[]>();

        if (true == this.OpenConnection())
        {
            MySqlCommand command = new MySqlCommand(selectQuery, connection);
            MySqlDataReader resultReader = command.ExecuteReader();

            while (resultReader.Read())
            {
                object[] resultRow = new object[resultReader.FieldCount];
                resultReader.GetValues(resultRow);
                resultList.Add(resultRow);
            }

            resultReader.Close();
            this.CloseConnection();
        }
        else
        {
            throw new Exception("Can not open connection to database.");
        }
        return resultList;
    }
}