How to detect Updated textbox with Linq - vb.net

-->VB.Net VS2010
If this is a stupid question, then let me know. I can't just figure it out.
First of all, this is my question. How do I detect the changed value on those text boxes?
I have an idea that I create a another string values that have the original values and compare them right before saving or form closing event. This sample just have 3 text boxes, but I have 50 + text boxes on my one form. I can do it that way, but that is not really smart idea.
Can I use abcDB.SubmitChanges() to detect any data changes on text boxes?
Dim sqlQuery = (From obj in abcDB.HelloWorld
Select obj.Fname, obj.Lname, obj.PhoneNumber).FirstOrDefault()
me.textboxFname.text = sqlQuery.Fname
me.textboxLname.text = sqlQuery.Lname
me.textboxPhoneNumber.text = sqlQuery.PhoneNumber

What you really want to do is called 'data binding'. Lots of tutorials about that aroud the web and any book about VB.NET will have at least 1 chapter dedicated to it.

Related

Fill a boolean array from checkbox control array

My program creates an array of checkboxes at runtime as shown below:
For Looper = 0 To 36
Dim Ex1ConfigCheck As New CheckBox
frmSetup.Controls.Add(Ex1ConfigCheck) ' Add Control to from
Ex1ConfigCheck.Top = (Looper + 45) + (Looper * 18) ' Set Location
Ex1ConfigCheck.Left = 210
Ex1ConfigCheck.Text = Setup.ExCheckName(Looper) ' Set Text property from strArray
Next
This is where I don't know how to proceed.
I would like to fill a boolean array (ex. MyBoolean(37)) with the value of Ex1configCheck().Checked. The reason I would like to fill another array is because I need to be able to reference the value of the checkboxes in other parts of the code but can't access them until they are created. Also, I plan on saving the array out to a binary file.
Could someone point me in the right direction please?
If there are no other CheckBoxes in the same container as those ones then you can do this:
Dim flags = Me.Controls.OfType(Of CheckBox)().
Select(Function(cb) cb.Checked).
ToArray()
If the controls are in a different container than the form itself, replace Me with that container.
As suggested by #Jimi, you could also create a List(Of CheckBox) and assign that to a field, populating it when you create the controls. You can then use that list instead of creating one on demand:
Dim flags = myCheckBoxList.Select(Function(cb) cb.Checked).
ToArray()
Of course, if you know exactly how many CheckBoxes you are going to be adding, why do you need to wait until run time to create them? Why can't you create them at design time and then modify them at run time? You usually only create controls at run time if you don't know how many there will be until run time, but that seems not to be the case here.
Thanks all for your answers and comments. I always have a fear of being roasted when I ask what some may consider a simple question online.
I have found an alternative way of accomplishing my task. Instead of creating 8 "Arrays" of checkboxes, I have learned of a very simple control available called "CheckedListBox".
I really didn't need to create the checkboxes at runtime but was trying to find an easier way to create 8 groups of 37 checkboxes without having to manually name and set the properties of each one during design. I also wanted to be able to index them in my code to be able to update and read the value using simple loops. I could have done this by creating arrays of CheckBox but again, I would have had to manually initialize the arrays.
Once I found the CheckedListBox, I was able to accomplish what I want very quickly. I only had to set the properties of the 8 "groups" (CheckedListBox's) and fill them using the items property. The ListBox essentially created a List like Jimi suggested automatically and I can index thru each list with a loop as desired. Jimi's suggestion actually lead me to finding the CheckedListBox while I was searching for more information on using "List(of CheckBox)".
Sometimes talking to others helps me find the right questions to ask. Google was able to figure out what I wanted when I searched for "List(of CheckBox)". (:

Spotfire: Need to select all values in a Multi select List Box Document Property

I have zero knowledge of coding. Can someone please help me with code.
My situation is as follows:
Dashboard has a Multi select List Box (Document Property). I am using that to restrict the data and calculations.
User does not want to select values each time. He wants a button where in (s)he click it once and all the values present in the list box gets selected.
Can someone please help me.
Regards,
Subro
This is fairly easy to do. Let us say that the Document Property that the list box is used for is named "Test" and it is of type "String List". Then you can use an IronPython script like so:
Document.Properties["Test"] = ["First Choice","Second Choice","Third Choice"]
Where the string list you see above, are all the values in your list box. Make sure that the strings you assign to the document property are the ones you want to populate your list with, since sometimes the displayed values can be different than the ones assigned to the document property(The case of using the "Fixed Values" option when setting up the control).
Hope that this helps.
Zenios

How to allow a combobox to be left blank//skipped on a form

I am relatively new to Access and any SQL and VBA I have picked up is self-taught, so I would really appreciate answers that are not too heavily laden with technical terms...that said, I am having an issue with allowing comboboxes to be left blank on a form if the user chooses not to input data. Also, I am using Access 2016.
Initially the problem I ran into was that if a combobox was entirely skipped and left blank, or if the user selects the combobox and then tries to move on without making a selection from the list, they got the error "You tried to assign the Null value to a variable that is not a Variant data type," and were unable to move on to any other fields on the form or to save the record being entered.
I found this article that details a possible solution, but I can't seem to get it to work. I made an unbound combobox, set the Row Source to:
SELECT EmailID, PersonalEmail FROM EmailT UNION SELECT "<N/A>","<N/A>" FROM EmailT
ORDER BY PersonalEmail;
where PersonalEmail is a field of type short text and the EmailID is an autonumber. I also followed the article's steps for formatting the combobox (column width, etc.) and set it to Limit to List = Yes.
Here is my exact code:
Private Sub Combo62_AfterUpdate()
If Combo62 = "<N/A>" Then
EmailID = Null
Else
EmailID = Combo62
End If
End Sub
Private Sub Form_Current()
If IsNull(EmailID) Then
Combo62 = "<N/A>"
Else
Combo62 = EmailID
End If
End Sub
< N/A> now shows up on my list, but if it is selected I get the error: "The value you entered isn't valid for this field. For example, you may have entered text in a numeric field or a number that is larger than the FieldSize setting permits."
Access's debugger highlights the line:
EmailID = Null
but I am not sure what steps I should take now to try and fix this.
I am completely open to other methods of allowing the combobox to be left blank if someone knows of a better way to do this also. For all I know, I am missing something really obvious! Thanks in advance for any insight!
EDIT: Thanks for your help guys, I never did figure out what exactly the problem was, but I got some advice from another forum to rethink my database design so this ended up being a null issue--it's all totally different now!
If the recordsource for your form contains a query with one-to-many relationships this error may come up. Try to use only the base table as the recordsource for the form. Use subforms if you need to display related data. The rest of the code may then be unnecessary.

Searching a bound Combo Box for User Input

Alright Gents,
Im trying to search a vb.net combo box for an item. The combo box is already bound to dataset. The display member is set to display just a single column of the selected record. I had it set initially so the objects displayed in the combo were a customized class. In this class I specified all the properties I wanted to keep track of and that seemed to work well. However now that I am using the combo box in its bound state it is much more difficult to manipulate the data.
Mission:
To have the user type a number, if the number is contained in the ComboBox, the combo box should then move to that record so that all the other items bound to that control will update as well.
Research:
I have looked into the System.Windows.Forms.BingingManagerBase class and that seems to have the information I need. I just can't figure out the bridge between that and what I'm trying to do. I want to throw something together so I tried to simply do a SQL search against the dataset for the text in the combobox. Unfortunately that requires late binding and my targeted version of the .Net compact framework does not support that.
Here is an example of the late binding I was attempting. (Im working with VB.net 2005, Compact Framework 3.5 I believe:
For i as integer = 0 to combobox.items.count - 1
dim Dsr as Dataset.Row
dim dv as dataview
Dsr = DirectCase(Dv.row, Dataset.Row)
If Dsr(i).DesiredColumn = DesiredRow.Desiredcolumn then
'Do such and such code
End If
Next
I want to be able to search the dataset for a specific record matching a query. After I find that row matching the query I want to be able to move my combo box to the row found in the SQL query. The main problem seems to be that the Combo works in Datarowviews and my datasets are mostly cast to rows pertaining to the DS.
Anyone have some insight on this it would be much appreciated.
Thanks again!
If you know the item that should be set as selected in the combobox you can just set the ComboBox.SelectedItem Property
If you actually do really need to loop through all the items bound to the combobox then once you reach the correct one you can set the ComboBox.SelectedIndex Property.
For i As Integer = 0 To ComboBox.Items.Count - 1
Dim drv As System.Data.DataRowView = Nothing
Dim desiredColumn As String = String.Empty
drv = DirectCast(ComboBox.Items.Item(i), DataRowView)
desiredColumn = Convert.ToString(drv("Tag"))
Debug.WriteLine(desiredColumn)
Next
This seems to find the column value for every record in the combo box allowing me to find the correct index of the text I am searching for. Like I said though, if I could find a way to search through the list of items in the combobox without having to address each one, I would be grateful.

ComboBox that remembers recently entered values and can autocomplete

I'm developing a Desktop Search Engine in VB.NET
I'm using a ComboBox to specify the search query (string).
I want the ComboBox to remember and display recent queries.
I also want the ComboBox to try and Autocomplete the queries as the user is typing.
What is the best way to implement this?
This can no doubt be done more elegantly, but here's the basic principles (apologies for any syntax issues, I'm not much of a VB guy):
In the KeyUp event:
Make sure the key in't a navigation key:
if e.KeyCode <> Keys.Back [...]
Search the items list for the text typed:
idx = myCombo.FindString(myCombo.Text)
Take the combo's found item:
s = myCombo.GetItemText(idx)
insert it into the .Text property:
myCombo.Text = s
Note that this would overtype everything the user entered (destroying case). You could improve this by appending the 'missing' part instead:
stringToAppend = s.SubString(myCombo.Text.Length)
myCombo.Text = myCombo.Text + stringToAppend
Finally, select the new text so they can keep typing:
myCombo.SelectionStart = myCombo.Text.Length - stringToAppend.Length
myCombo.SelectionLength = stringToAppend.Length
You might also want to look at this from vbAccelerator.com, offered as a basic starting point for auto-completion in VB.NET. The vbAccelerator code is usually high quality.