C#, SQL Server database, connection timeout. The timeout period elapsed prior to obtaining a connection from the pool - sql-server

Question

I am using a connection class for my connection and then I call the class for connecting.
After I use the connection several times it freezes and then gives a error. It seems I have got to many connections open at the same time I can't figure out how tho close the open connections. If that is the real problem.
MyConnection class:
public class MyConnection
{
private SqlConnection _con;
public SqlCommand Cmd;
private SqlDataAdapter _da;
private DataTable _dt;
public MyConnection()
{
_con = new SqlConnection("Data Source=192.168.1.12\\grs;Initial Catalog=BGI;Persist Security Info=True;User ID=awplanung;Password=pass");
_con.Open();
}
public void SqlQuery(string queryText)
{
Cmd = new SqlCommand(queryText, _con);
}
public DataTable QueryEx()
{
_da = new SqlDataAdapter(Cmd);
_dt = new DataTable();
_da.Fill(_dt);
return _dt;
}
public void NonQueryEx()
{
Cmd.ExecuteNonQuery();
}
}
And now I call this connection from my forms: like this one.
MyConnection con = new MyConnection();
con.SqlQuery("SELECT ARartikelnr ,ARartikelbezeich, ARartwarengruppe, ARanzahleinheiten, ARinhalteinheiten, ARanzgebindepal FROM BGARTIKEL where ARartikelnr BETWEEN '" + textBox2.Text + "' and '" + textBox3.Text + "' order by ARinhalteinheiten, ARartwarengruppe");
dt = con.QueryEx();
Each time I open a new form I make a
MyConnection con = new MyConnection();
and make many similar
con.SqlQuery("Select string")
After I open a second form it freezes when I do a new long select. What is strange is that I have used these 2 forms without problems, but in the first one I made a datagrid fill with a button. and now i changed if to fill directly from the form load. and when i go to the next form i cant fill my other datagrid on the new form giving that error.
Error:
Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.

Answer 1

Make your MyConnection class disposable. And dispose it when you are done with data.
implement IDisposable interface on class
(public class MyConnection : IDisposable)
implement Dispose method where dispose your connection
public void Dispose()
{
_con.Dispose();
}
and use it like this
using(MyConnection con = new MyConnection())
{
con.SqlQuery("...");
dt = con.QueryEx();
}