Hi,
hi,its glad to tell i saved spinner value(courseNumbers) in database with ur
assistance code...but when i click on retreive button now i want to populate
that spinner with courses based on the value(courseNumber) in database based
on sno...
ex data in database:
sno course address
1000 303 uk
1001 404 india
1002 505 usa
here my requiremnt is when i give value in sno edittext and click on
retreive button the data should populate in spinner and edittext....for
example i enter 1000 in sno edittext and click on retreive button the
spinner should populate with Biology and address edittext sholud populate
with uk....the spinner should set with coursename based on courseNumber in
database...
This is where the use of a dictionary object comes in handy. My original
code constructed two Lists (an int and string) which contained the
course names and course values. This was fine for my demonstration
purpose, but now we're doing searches. Of course, you can do them on
List objects and we'll use both so you can decide which works best.
A dictionary has the advantage of being a key/value system, I have a key
(say "German") and this has an associated value (505). To set up the
dictionary...
Dictionary <keyType, valueType> name = new Dictionary<keyType, valueType>();
where keyType is the type of object the key is (for example, string,
int, double, class, List<T> etc) and valueType is the type of object the
value is (string, double etc).
As with a List, you add to the dictionary using the .Add method, so if I
have a Dictionary<string, int> foo, it would be
foo.Add("German", 505);
There are plenty of ways to get values out of the dictionary object, but
possibly the most useful for you will be to use TryGetValue. This looks
up a given key in the dictionary and returns a value.
To get a value from foo...
int outValue = 0;
if (foo.TryGetValue("German", out outValue))
Console.WriteLine("value found = {0}, outValue);
else
Console.WriteLine("key not found");
There is a very slight performance hit using a Dictionary; it is
slightly slower than searching a list, but consider this. If I want to
search a list for a string, I can do this
if (foo.Contains("German"))
but then I have to find where in the list "German", so the code becomes
int position = 0;
if (foo.Contains("German"))
{
position = foo.IndexOf("German");
Console.WriteLine("position of German = {0}", position;
}
else
Console.WriteLine("German not found");
In effect, there are two lookups. I've not done any sort of performance
timing on using this "double lookup", but I'd expect it now to be slower
than a dictionary.
conn.Open();
SqliteDataReader sdr = cmd.ExecuteReader();
while (sdr.Read())
{
string str = Convert.ToString(sdr["SCOURSE"]);
/* here have to write the code for population of
spinner ....here i have taken courseNumber in string variable str...based on
this value spinner should set with course... */
Here then you would want to be using Dictionary<int, string>
the parameter to search though would need to be an int, so
int strToFind = Convert.ToInt32(sdr["SCOURSE"]);
then
if (myDictionary.ContainsKey(strToFind))
etaddspinner.Text = Convert.ToString(sdr["SADD"]);
However, as you're just drawing from the database rather than anything
else, you can ignore the dictionary and use the list as before. Again
though, you will need to be using an int to look up the course number,
so the code would be
int strToFind = Convert.ToInt32(sdr["SCOURSE"]);
if (myCourseList.Contains(strToFind))
etaddspinner.Text = Convert.ToString(sdr["SADD"]);
At this point you may be wondering how to make this even more flexible.
That's simple, follow this logic
1. Set up your container(s) (either List<> or Dictionary)
2. Read in from the database the available courses and course numbers
into the containers
3. That's it
Once you've read in from the database to propagate the containers, you
don't need to do it anymore. Database access slows things down big time!
Paul
--
"Space," it says, "is big. Really big. You just won't believe how
vastly, hugely, mindbogglingly big it is. I mean, you may think it's a
long way down the road to the chemist's, but that's just peanuts to
space, listen..."
Hitch Hikers Guide to the Galaxy, a truly remarkable book!
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