F# Inherit from C# class + access protected fields

问题

I have this base class that creates a new SQL Server connection and does some utility methods in C#, I want to inherit in F#. Currently I cannot access the protected fields in the C# class from F#, although this would work in C#.

C# abstract class

public abstract class SQL
{
    protected readonly SqlConnectionStringBuilder bld;
    protected readonly SqlCommand cmd;
    protected readonly SqlConnection conn;
    protected readonly string connstring;
    protected string userid;

    public SQL(string server, string db)
    {
        bld = new SqlConnectionStringBuilder();
        bld.DataSource = server;
        bld.InitialCatalog = db;
        bld.IntegratedSecurity = true;
        connstring = bld.ConnectionString;

        conn = new SqlConnection(connstring);
        cmd = new SqlCommand();

        GetUserID();
        //Other utility methods here
    }

F# code to inherit

type Transfer ( server : string ) ( db : string ) = 
inherit SQL(server, db)  
let accessAbstractConn = conn. //Can't access protected field????

Have I missed something here? I have tried aliasing the base class field e.g. this.conn which also does not work.

Thanks Richard

回答1:

You can add a self-identifier to the constructor:

type Transfer ( server : string, db : string ) as this = 
  inherit SQL(server, db)  
  let accessAbstractConn = this.conn

or, use the base keyword:

type Transfer ( server : string, db : string ) = 
  inherit SQL(server, db)  
  let accessAbstractConn = base.conn

回答2:

See related questions:

F# - How to access protected member
Why isn't there a protected access modifier in F#?

Basically I think you can't do it from within a let because it's actually in the context of an implicit lambda.

来源：https://stackoverflow.com/questions/15091468/f-inherit-from-c-sharp-class-access-protected-fields

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inheritance

protected