help to adding variable to list of string

diamond diamond

12y1.7kVisual Basic .NET

Hello

I have such a code but it does not work. say db.count=0 and does not show its values.

var data_bot = bot_list.Intersect(da);
List db = new List();
db = data_bot.Select(sss => sss.ToString()).ToList();

11 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes12y ago
Accepted answer
Well, if I run this extra line:

foreach(string s in da) Console.WriteLine(s);

then the output is again:

1
2

so I'd check first of all that you've copied the code correctly.

If you have, then some of the strings in 'da' can't be exactly of this pattern:

{source=ddd}

in particular there could be white-space at either side of the equals sign. If there is, then try re-ordering the Replace statements to remove white-space first:

da = da.Select(s => s.Replace(" ", "").Replace("{source=", "").Replace("}","")).ToList();
+1
diamond diamond12y ago
Thanks Valpes, Just the last } has been removed like {"source=1"
0
Vulpes12y ago
OK, this code will do that:

var Bot_list= new List{"1","2","3"};
var da = new List{"{source=1}","{source=2}"};
da = da.Select(s => s.Replace("{source=", "").Replace("}","").Replace(" ", "")).ToList();
var db = Bot_list.Intersect(da).ToList();
foreach(string s in db) Console.WriteLine(s);

Output as before:

1
2

0
diamond diamond12y ago
Yes first they are removed, then the intersect operate on them
0
Vulpes12y ago
Do you want to remove those extra characters from 'da' itself?
0
diamond diamond12y ago
Thanks so much Vulpes, But it does not remove extra charecters like "{source=}
0
Vulpes12y ago
This shorter version is also working:

var Bot_list= new List{"1","2","3"};
var da = new List{"{source=1}","{source=2}"};
var db = Bot_list.Where(n => da.Any(s => s.Contains("{source=" + n + "}"))).ToList();
foreach(string s in db) Console.WriteLine(s);
0
Vulpes12y ago
The Intersect method is not working because the strings are not the same - you need to know whether one includes the other.

Try this instead:

var Bot_list= new List{"1","2","3"};
var da = new List{"{source=1}","{source=2}"};
var db = Bot_list.Where(n =>
{
foreach(string s in da)
{
if (s.Contains("{source=" + n + "}")) return true;
}
return false;
}).ToList();

foreach(string s in db) Console.WriteLine(s);

which gives output of:

1
2

0
diamond diamond12y ago
Hi Thanks for your responses. I found my error by I could not solve it. Bot_list={"1","2","3"}; da={"{source=1}","{source=2}"} for these charectares in da list "{source}", it does not show intersects. Please help me
0
Vulpes12y ago
Well, I don't see any 'logic' error in your code. Whatever objects data_bot contains, a list will be produced of their string equivalents and assigned to the variable 'db'.

Of course, if 'bot_list' and 'da' have no elements in common, then their intersection will be empty and so too will the string list. So if you're unexpectedly getting an empty list, are you sure that its the intersection you wanted and not the union?

Incidentally, one thing you shouldn't do is this:

List db = new List();
db = data_bot.Select(sss => sss.ToString()).ToList();

Instead, just do:

List db = data_bot.Select(sss => sss.ToString()).ToList();

The problem with the first approach is that it creates a new List object which immediately becomes eligible for garbage collection when you assign a reference to a new List object to the variable 'db' in the next line.

This just uses up memory and the GC's time needlessly.
+1
Ramesh Maruthi12y ago
Hey Diamond Diamond,

What exactly do you get in data_bot ?
var data_bot = bot_list.Intersect(da);
db = data_bot.ConvertAll(sss =>Convert.ToString(sss));

otherway:

db =(data_bot.First() as Object[]).ToList().ConvertAll(sss =>Convert.ToString(sss));
0