C#连接sqlite数据库

　web.config　

public class ProductService
{
public static readonly ProductService Instance = new ProductService();
private static string cOnnstr= ConfigurationManager.ConnectionStrings["SQLiteDB"].ConnectionString;

public DataTable GetData()
{
SQLiteConnection cOnn= null;
int num = 0;
int productNum = 10;
try
{
cOnn= new SQLiteConnection(connstr);
conn.Open();
string sql = "select * from users";
//SQLiteParameter[] parameter = { new SQLiteParameter("@product", product), new SQLiteParameter("@productNum", productNum) };
SQLiteCommand cmd = new SQLiteCommand(sql, conn);
//cmd.Parameters.AddRange(parameter);
SQLiteDataAdapter sda = new SQLiteDataAdapter(cmd);
DataTable dt = new DataTable();
sda.Fill(dt);

return dt;
}
catch (Exception ex)
{
return null;
}

}
}