TextBox AutoComplete Not working properly

Question

I am trying to implement a textbox autocomplete with a custom datasource in the form of an array which shows suggestions on single character input. But when i run the program the autocomplete only starts after the second character input. When i debugged i saw that datas are there in the AutoCompleteNameCollection but it is not showing in the suggestion until the second character input.

This code i have written in the textchange event.

arr = LoadName(empid_txt.Text.Trim());  //arr is string array                          
namesCollection.AddRange(arr);
this.empid_txt.AutoCompleteMode = AutoCompleteMode.Suggest;
this.empid_txt.AutoCompleteSource = AutoCompleteSource.CustomSource;
this.empid_txt.AutoCompleteCustomSource = namesCollection;

In the LoadEvent I have initialized the AutoCompleteNameCollection with an empty array.

namesCollection.AddRange(arr);// here arr is empty
empid_txt.AutoCompleteMode = AutoCompleteMode.Suggest;
empid_txt.AutoCompleteSource = AutoCompleteSource.CustomSource;
empid_txt.AutoCompleteCustomSource = namesCollection;

But it does't work until the second character input. However if instead of an array i initialize the AutoCompleteNameCollection with an empty string like : namesCollection.Add(""); it does work for the single character input but some times it gives AccessViolationException: Attempted to read or write protected memory. So is there any way i can solve this problem?

I had the same problem with textbox, for me i was using multiline with textbox which was causing this issue. Changing multiline to false solved the issue. — Huzaifa, Nov 05 '20 at 14:43

score 2 · Answer 1 · answered Mar 12 '12 at 18:17

I can replicate the access violation when setting the AutoCompleteSource in the event handler, it seems like the autocomplete routine may be accessing the AutoCompleteSource while it is being replaced and destroyed.

To prevent this you can put a lock around your code.

lock(this)
{
arr = LoadName(empid_txt.Text.Trim());  //arr is string array                          
namesCollection.AddRange(arr);
this.empid_txt.AutoCompleteMode = AutoCompleteMode.Suggest;
this.empid_txt.AutoCompleteSource = AutoCompleteSource.CustomSource;
this.empid_txt.AutoCompleteCustomSource = namesCollection;
}

This stopped the access violations.

John Woo · Answer 2 · 2012-03-11T01:35:14.767

1

AutoComplete suggests after the second char is being pressed is normal because in the first place, you have initialized the arr (which is your custom datasource) into an empty array. You have populated your arr in TextChanged event and that's why AutoComplete works at the second char because your datasource is filtered based on your first char (which is definitely what you don't want).

Here's a suggestion:

On the FormLoad event of your application, fill arr with all the possible suggestions (I think the source of suggestion is from database right?). This will allow textbox to suggest on your first char.
When you have entered the first char, on the TextChanged event reload your arr datasource based on the prevous character being entered.

Hope it helps.

edited Mar 11 '12 at 01:35

answered Mar 11 '12 at 01:27

John Woo

258,903
69
498
492

I don't wanna put everything in form load event ...it causes too much network congestion and requires a significant amount of bandwidth when the data to be retrieved is huge so I am using text changed event only...furthermore as i said it does work for single character input when i initialize it in the form load event with an empty string first and then change the data source to a string array in text changed event...but it is not stable as it sometimes gives exception as mentioned above. And yeah the data source is in fact a database. – Nav Mar 11 '12 at 02:43

score 1 · Accepted Answer · answered Mar 13 '12 at 13:06

On load you may populate the TextBox with a sub-set of your data (that can be even cached for future/shared use). If you have a "most common" counter you can use it. As limit condition you may even add a dummy item (if what you get with an empty string is an access violation). Then, on the TextChange event read the data you need from the database.

I have only one question: you do not want to populate the source until the user starts to type? If there's the problem of network traffic then you move a lot of data. If you move a lot of data then your users will have to wait when they start to type something. Is it acceptable? On the other side if they do not wait too much maybe data stream is not so big and you can put that logic in a BackgroundWorker in the constructor of your form (or not far from that time).

Dipanki Jadav · Answer 4 · 2014-03-10T10:02:46.010

On Form Load call the Textbox autocomplete method.

 public void autocompleteData()
    {
            //SuggestStrings will have the logic to return array of strings either from cache/db
            var CurrentuserId = CloudKaseWSClient.GetUserDetail(tokenUsr, tokenPasswd, Username);
            List<string> l = new List<string>();
            var SearchResults = ("Select Database Query").ToList();
            foreach (var i in SearchResults)
            {
                l.Add(i.name);
            }
            string[] arr = l.ToArray();
            AutoCompleteStringCollection collection = new AutoCompleteStringCollection();
            collection.AddRange(arr);

        txtSearchUser.AutoCompleteMode = AutoCompleteMode.SuggestAppend;
        txtSearchUser.AutoCompleteSource = AutoCompleteSource.CustomSource;
        txtSearchUser.AutoCompleteCustomSource = collection;
    }

OR You want to set static data for AutoComplete Textbox than you have to set In Design view for Textbox property of AutocompleteMode to set SuggestAppend,AutocompleteSource to set CustomSource and add static value inAutocompleteCustomSource.

I hope this solution helps to you.. Happy Coding.:)

score 0 · Answer 5 · answered Feb 28 '12 at 18:57

0

If 'arr' is empty when you initialize the textbox then there is nothing to compare to. You have to initialize AutoCompleteCustomSource to a valid array before you start typing. You are initializing in textchange event, when the user has already typed a character.

You need to populate the namesCollection before the code is changed - in Initialize.

answered Feb 28 '12 at 18:57

Raj Ranjhan

3,869
2
19
29

Are you asking me to load all the data before the user starts typing. If so that i can't do because there are lots of data which i can filter in the textchange event. – Nav Feb 28 '12 at 19:38
Until it has something to match against, the textbox cannot autocomplete. Since you do not populate the source until after the user has typed something, it won't autocomplete on first character. You can try filtering on of the upstream events(i.e.KeyDown event) – Raj Ranjhan Feb 28 '12 at 21:03
but it does work when i initially populate the source with a empty string instead of a string array and later replace/append it with a string array in text change... but,sometimes it gives access violation exception . Do u know any work around ?? – Nav Feb 29 '12 at 06:40

TextBox AutoComplete Not working properly

5 Answers5

Linked