recursive function in c# get a parameter

Question

I'm trying to get a parameter with this function...

public static int subsumer(string id,int acc,SqlConnection connection) 
{
    acc++;
    SqlCommand cercas = new SqlCommand("select * from common_relation where id_source ='" + id + "' AND type='@' ", connection);
    SqlDataReader leggsyn = null;
    leggsyn = cercas.ExecuteReader();

    int f = 0;
    while (leggsyn.Read()) 
    {
        f=  subsumer(leggsyn["id_target"].ToString(),acc,connection);
        if (acc <= f) 
        { 
            acc = f; 
        }  
    }

     //siamo arrivati alla fine
    return acc-1;
}

each cycle the parameter acc will increment and debugging i see that in my case it reach value 3, but in the final recursion i get always 0...i can't get it...thank you all

What do you mean by parameter? Also why are you using string concatenation instead of using a proper parameterized query? A single weird character in your inputs will cause problems. More interesting input may be 1;DROP TABLE COMMON_RELATION;-- — Panagiotis Kanavos
– Panagiotis Kanavos, Commented Apr 1, 2015 at 14:29
How are you calling the function? Have you stepped through it in the debugger to make sure your logic is correct? — D Stanley
– D Stanley, Commented Apr 1, 2015 at 14:31
what is your function suppose to do ? sum or max ? because i see only assignation in your loop no incrementation — Emmanuel M.
– Emmanuel M., Commented Apr 1, 2015 at 14:43
i'm calling this function this way int fuffa = DistanzaParole.subsumer("n#00004123", 0, connection); it is supposed to give me the max acc it can reach — Lorenzo
– Lorenzo, Commented Apr 1, 2015 at 14:48

Radin Gospodinov · Accepted Answer · 2015-04-01 14:28:55Z

2

You need to pass acc by reference. I.e use: public static int subsumer(string id,ref int acc,SqlConnection connection) {

answered Apr 1, 2015 at 14:28

Radin Gospodinov

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2 Comments

D Stanley Over a year ago

The function is returning acc-1 so using ref should not be necessary (unless the OP is calling it incorrectly).

Lorenzo Over a year ago

i'm calling this way int fuffa = DistanzaParole.subsumer("n#00004123", 0, connection);

Guillaume · Accepted Answer · 2015-04-01 14:52:46Z

1

By returning acc - 1, you are decrementing f returned by your recursive call and I don't think that's what you expect.

public static int subsumer(string id,int acc,SqlConnection connection) 
{
    SqlCommand cercas = new SqlCommand("select * from common_relation where id_source ='" + id + "' AND type='@' ", connection);
    SqlDataReader leggsyn = null;
    leggsyn = cercas.ExecuteReader();

    int f = 0;
    while (leggsyn.Read()) 
    {
        f=  subsumer(leggsyn["id_target"].ToString(),acc + 1,connection);
        if (acc <= f) 
        { 
            acc = f; 
        }  
    }

     //siamo arrivati alla fine
    return acc;
}

On a side note, querying recursively isn't a good design choice. Querying recursively with readers open for each call on the stack is even worse. Not using query parmeters is also a bad thing.

answered Apr 1, 2015 at 14:52

Guillaume

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2 Comments

Lorenzo Over a year ago

ok now i finally get it! i know query recursively isn't a good choise, i'm not an expert developer and i'm facing sentence similarity with wordnet and some other stuff that it isn't properly an "hello world". How can i use query parameters?

Guillaume Over a year ago

@Lorenzo, search existing questions or post a new one containing your query and asking how you can parameterize it.

Andy Wiesendanger · Accepted Answer · 2015-04-01 14:51:25Z

0

The method increments at the beginning, and decrements at the end, therefore it seems you will always end up at the initial call value of acc (in your case, 0).

answered Apr 1, 2015 at 14:51

Andy Wiesendanger

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2 Comments

Lorenzo Over a year ago

it is not supposed to increment in: f= subsumer(leggsyn["id_target"].ToString(),acc,connection); if (acc <= f) { acc = f; } ?

Andy Wiesendanger Over a year ago

It will increment when acc++, then when there are no records, it will return acc--, which means it returns the same value it was given.

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