Postgres analog for c# SQL Server´s stored procedure CLR

It is know that SQL Server offers some extensibility mechanisms like user-defined functions, stored procedures, triggers...

I have C# code that runs in SQL Server 2008 (it is a stored procedure that is deployed in the DBMS using Visual Studio 2008, and then a exec dbo.SP_Analysis 'MyTable','Colum1,Column2',300,0 command is used to get the results in SQL Server 2008) defined as:

using System;
using System.Collections.Generic;
using System.Text;
using System.Security;
using System.Runtime.InteropServices;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;

public partial class StoredProcedures
{              
  [Microsoft.SqlServer.Server.SqlProcedure]
  public static void SP_Analysis(
     SqlString table, [SqlFacet(MaxSize = -1)] SqlString columns,
     int Nocustomers,
     Boolean result)
  {
     String query = "";

     using (SqlConnection conn = new SqlConnection("context connection=true"))
     {
        conn.Open();
        SqlCommand cmd = conn.CreateCommand();
        query = "SELECT " + (String)columns + " FROM " + (String)table + ";";
        cmd.CommandText = query;
        SqlDataReader reader = cmd.ExecuteReader();
        MyObject _myObject = new Object(Nocustomers);
        while (reader.Read())
           _myObject.read(reader);
        reader.Close();        
        conn.Close();
      } //END SqlConnection conn 
  }        
}

class MyObject
{
   int NoCustomers; 
   //some definitions

  public MyObject(int NoCustomers)
  {
     this.NoCustomers = NoCustomers;
     //some stuff
  }

   public void read(SqlDataReader reader)
   {
     Object[] record = new Object[NoCustomers];
     reader.GetValues(record);
     //more stuff
   }
}

It is clear that I am using .NET c# available language and then deploy it to create a stored procedure in SQL Server 2008, via Visual Studio 2008.

Now my question is what is the analog to all this in Postgres?

1. What language is available to extend the functionality of Postgres?
2. What is the analog of Visual Studio to have the possibility to deploy a UDF in Postgres?
3. What is the analog of exec dbo.UDF in Postgres?

I was reading that Postgres uses C language to define UDFs maybe C++ but the others I have no idea...