Question

I am trying to write a function that can take three parameters: an SqlDataReader, a DataGridView and a List.

I want to take the contents of the SqlDataReader and create a list of Objects, then bind this to the DataGridView.

With a few pointers from another Stack Overflow user I came up with the following:

public void FillArrayList<T>(DataGridView grid, SqlDataReader reader, List<T> list)
{
    //Fill the list with the contents of the reader
    while (reader.Read())
    {
        Object obj = new Object();
        Type type = typeof(T);

        FieldInfo[] fields = type.GetFields(); // Get the fields of the assembly
        int i = 0;

        foreach(var field in fields)
        {
            field.SetValue(obj, reader[i]); // set the fields of T to the reader's value
            i++;
        }

        list.Add((T)obj);
    }

    grid.DataSource = list;
}

When I run the code, I get an error when casting the object to type T:

Unable to cast object of type ‘System.Object’ to type
‘TestHarness.Organisation’.

I was under the impression that an Object could store anything. Can anyone advise me on why this cast cannot be performed?

Thanks,

Andy

Answer 1

With a little help from the link posted by MMK, in the comment below my question, I have devised a solution:

public void FillList<T>(DataGridView grid, string SQLCommand, List<T> list) where T : class, new()
    {
        //Load the data into the SqlDataReader
        SqlCommand dataCommand = new SqlCommand();
        dataCommand.Connection = dataConnection;
        dataCommand.CommandType = CommandType.Text;
        dataCommand.CommandText = SQLCommand;

        SqlDataReader dataReader = dataCommand.ExecuteReader();

        //Fill the list with the contents of the reader
        while (dataReader.Read())
        {
            var obj = new T();

            //Get the property information
            PropertyInfo[] properties = typeof(T).GetProperties();
            int i = 0;

            foreach(var property in properties)
            {
                property.SetValue((T)obj, dataReader[i], null); // set the fields of T to the reader's value
                i++;
            }

            list.Add(obj);
        }

        dataReader.Close();

        //Bind the list to the DataGridView
        grid.DataSource = list;
    }

Seems to do exactly what I need. It’s possible I may come across some obvious error as I use this in more and more situations, but, this is life.

Thanks for your help, guys!