Question

I’m a vb.net guy trying to figure out MonoTouch c#.

I made this data helper:

public static void ExecuteCommand (SqliteConnection cnn, string command, System.Data.Common.DbParameterCollection parameters)
{
    using (var c = cnn.CreateCommand()) {
        c.CommandText = command;
        c.CommandType = CommandType.Text;
        foreach (var p in parameters)
        {
            c.Parameters.Add (p);
        }
        c.ExecuteNonQuery ();
    }
}

And now I want to call the ExecuteCommand…

var parameters = new System.Data.Common.DbParameterCollection();
parameters.Add("@1", DbType.String).Value = "test";
DataConnection.ExecuteCommand ("INSERT INTO mytest (name) VALUES (@)", parameters);

But MonoTouch says…

• var parameters = new System.Data.Common.DbParameterCollection(); <– “Cannot create an instance of the abstract class or interface ‘System.Data.Common.DbParameterCollection'”

• parameters.Add(“@1”, DbType.String).Value = “test”; <– “A local variable ‘parameters’ cannot be used before it is declared.”

I’m sure the answer is pretty easy, but comming from a VB.Net world, this is not obvious to me.

Answer 1

System.Data.Common.DbParameterCollection is abstract as such you cannot create it. You should be creating a (concrete( collection that inherits from it. In SQLite case it would be Mono.Data.Sqlite.SqliteParameterCollection.

Your second error is likely related to the first, since parameters could not be compiled correctly.