尝试在同一连接中运行多个命令时，C＃Winforms Npgsql 3.0.5“正在进行的操作”错误

I'm trying to run the following snippet in C# Winforms. This piece of code is working well with pgsql 2.2.6 adapter. What correction can be made in order to work fine with pgsql3.0.5 adapter? Thanks.I'm trying to run the following snippet in C# W