Develop Reference

The BindingList Datasource of a Combobox refreshes correctly but the Combobox displays items in the wrong order

I have a BindingList< KeyValuePair < string, string > > that is bound to a ComboBox control. Based on some conditions, the BindingList will be added a new KeyValuePair. Now, the Newly added item shows up at index 0 of the Combobox, instead of at the end.
While debugging, I found that the BindingList has got the right order. (i.e, the new KeyValuePair is appended)
Also, I check the SelectedValue of the ComboBox in it's SelectedIndexChanged handler and it seems to be not of the ListItem that got selected. Instead, it is that of the supposed ListItem, if the ComboBox had got the right order as in its DataSource, - the BindingList..
The code is a small part of a large project.. Plz let me know if the question is not clear. I can put the relevant parts of the code as per our context.
How could something like this happen? What can I do differently?
I have this class something like this.
public class DropdownEntity
{
//removed all except one members and properties
private string frontEndName
public string FrontEndName
{
get {return this.frontEndName; }
set {this.frontEndName= value; }
}
//One Constructor
public DropdownEntity(string _frontEndName)
{
this.FrontEndName = _frontEndName;
//Removed code which initializes several members...
}
//All methods removed..
public override string ToString()
{
return frontEndName;
}
}
In my windows form, I have a tab control with several tabs. In one of the tabs pages, I have a DataGridView. The user is supposed to edit the cells and click on a Next - button. Then, some processing will be done, and the TabControl will be navigated to the next tab page.
The next tab page has the combobox that has the problem I mentioned. This page also has a back button, which will take back.. the user can modify the gridview cells again.. and click on the next button. This is when the order gets messed up.
I am posting here the Click event handler of the Next Button.. Along with the class, with the rest of the code removed.
public partial class AddUpdateWizard : Form
{
//Removed all members..
BindingList<KeyValuePair<string, string>> DropdownsCollection;
Dictionary<string, DropdownEntity> DropdownsDict;
//Defined in a partial definition of the class..
DataGridView SPInsertGridView = new DataGridView();
ComboBox DropdownsCmbBox = new ComboBox();
Button NextBtn2 = new Button();
Button BackBtn3 = new Button();
//Of course these controls are added to one of the panels
public AddUpdateWizard(MainForm mainForm)
{
InitializeComponent();
DropdownsDict = new Dictionary<string, DropdownEntity>();
}
private void NextBtn2_Click(object sender, EventArgs e)
{
string sqlArgName;
string frontEndName;
string fieldType;
for (int i = 0; i < SPInsertGridView.Rows.Count; i++)
{
sqlArgName = "";
frontEndName = "";
fieldType = "";
sqlArgName = SPInsertGridView.Rows[i].Cells["InsertArgName"].Value.ToString().Trim();
if (SPInsertGridView.Rows[i].Cells["InsertArgFrontEndName"].Value != null)
{
frontEndName = SPInsertGridView.Rows[i].Cells["InsertArgFrontEndName"].Value.ToString().Trim();
}
if (SPInsertGridView.Rows[i].Cells["InsertArgFieldType"].Value != null)
{
fieldType = SPInsertGridView.Rows[i].Cells["InsertArgFieldType"].Value.ToString().Trim();
}
//I could have used an enum here, but this is better.. for many reasons.
if (fieldType == "DROPDOWN")
{
if (!DropdownsDict.ContainsKey(sqlArgName))
DropdownsDict.Add(sqlArgName, new DropdownEntity(frontEndName));
else
DropdownsDict[sqlArgName].FrontEndName = frontEndName;
}
else
{
if (fieldType == "NONE")
nonFieldCount++;
if (DropdownsDict.ContainsKey(sqlArgName))
{
DropdownsDict.Remove(sqlArgName);
}
}
}
//DropdownsCollection is a BindingList<KeyValuePair<string, string>>.
//key in the BindingList KeyValuePair will be that of the dictionary.
//The value will be from the ToString() function of the object in the Dictionary.
DropdownsCollection = new BindingList<KeyValuePair<string,string>>(DropdownsDict.Select(kvp => new KeyValuePair<string, string>(kvp.Key, kvp.Value.ToString())).ToList());
DropdownsCmbBox.DataSource = DropdownsCollection;
DropdownsCmbBox.DisplayMember = "Value";
DropdownsCmbBox.ValueMember = "Key";
//Go to the next tab
hiddenVirtualTabs1.SelectedIndex++;
}
private void BackBtn3_Click(object sender, EventArgs e)
{
hiddenVirtualTabs1.SelectedIndex--;
}
//On Selected Index Changed of the mentioned Combobox..
private void DropdownsCmbBox_SelectedIndexChanged(object sender, EventArgs e)
{
if (DropdownsCmbBox.SelectedValue != null)
{
if (DropdownsDict.ContainsKey((DropdownsCmbBox.SelectedValue.ToString())))
{
var dropdownEntity = DropdownsDict[DropdownsCmbBox.SelectedValue.ToString()];
DropdownEntityGB.Text = "Populate Dropdowns - " + dropdownEntity.ToString();
//Rest of the code here..
//I see that the Datasource of this ComboBox has got the items in the right order.
// The Combobox's SelectedValue is not that of the selected item. Very Strange behavior!!
}
}
}
}
The very first time the user clicks the Next Button, it's fine. But if he clicks the Back Button again and changes the Data Grid View cells.. The order will be gone.
I know, it can be frustrating to look at. It's a huge thing to ask for help. Any help would be greatly appreciated!
Please let me know if you need elaboration at any part.
Thanks a lot :)

I think you have two problems here.
First, if you want to retain the order of the items you should use an OrderedDictionary instead of a regular one. A normal collection will not retain the order of the items when you use Remove method. You can see more info about this related to List here.
You could use such dictionary like this:
DropDownDict = new OrderedDictionary();
// Add method will work as expected (as you have it now)
// Below you have to cast it before using Select
DropDownCollection = new BindingList<KeyValuePair<string, string>>(DropDownDict.Cast<DictionaryEntry>().Select(kvp => new KeyValuePair<string, string>(kvp.Key.ToString(), kvp.Value.ToString())).ToList());
The second problem could be that you change the display name (FrontEndName) of already existing items, but the key is preserved. When you add a new item, try to remove the old one that you're not using anymore and add a new item.

The Sorted Property of the Combobox is set to True! I didn't check that until now. I messed up. Terribly sorry for wasting your time Adrian. Thanks a lot for putting up with my mess here.. :)

Can someone tell me what's wrong with this code?

I'm trying to implement a search as you type (like in iTunes). I am using an ObjectListView. Further, I have a textbox that is used to do the search as shown below:
private void textBoxSearch_TextChanged(object sender, EventArgs e)
{
string txt = textBoxSearch.Text;
TextMatchFilter filter = null;
if (!String.IsNullOrEmpty(txt))
{
filter = TextMatchFilter.Contains(myObjectListView, txt);
}
// Setup a default renderer to draw the filter matches
if (filter == null)
myObjectListView.DefaultRenderer = null;
else
{
myObjectListView.DefaultRenderer = new HighlightTextRenderer(filter);
// Uncomment this line to see how the GDI+ rendering looks
myObjectListView.DefaultRenderer = new HighlightTextRenderer { Filter = filter, UseGdiTextRendering = false };
}
// Some lists have renderers already installed
HighlightTextRenderer highlightingRenderer = myObjectListView.GetColumn(0).Renderer as HighlightTextRenderer;
if (highlightingRenderer != null)
highlightingRenderer.Filter = filter;
myObjectListView.ModelFilter = filter;
}
Can someone figure out why this doesn't work?
The above code is meant to filter search results as the user types in the textbox (Like iTunes does, if you have ever used itunes). Apparently, up to this point, nothing happens. It seems like this code does not even execute.

Per this, the ObjectListView has a property named UseFiltering that is false by default and must be set to true to enable filtering.

Properties value resetting within another event

I am having some trouble with getting the formatting to occur correctly. I believe it stems from what is probably incorrect understanding of the events that I am attempting to make the changes in.
any direction would be great
private void so_FetchData(object sender, FetchEventArgs eArgs)
{
if (m_so != null && m_so.Rows.Count > (m_soRowCount + 1))
{
DataRow soDr = m_so.Rows[m_soRowCount++];
if (soDr != null)
{
var compResID = (int) soDr["CompResID"];
var result = (ComplianceLevel) soDr["Result"];
var sectNum = (int) soDr["JobSectType"];
var sectName = soDr["S" + sectNum + "Name"] as string;
var sectTxt = soDr["S" + sectNum + "Text"] as string;
Fields["CompLev"].Value = (result == ComplianceLevel.OtherThanSerious) ? "Other Than Serious" : result.ToString();
m_sectInfo = new SectInfo(sectName, sectTxt);
m_causes = new Causes(compResID);
m_actions = new Actions(compResID);
subReport1.Report = m_sectInfo;
subReport2.Report = m_causes;
subReport3.Report = m_actions;
eArgs.EOF = false;
}
}
else
{
eArgs.EOF = true;
}
}
private void eh_BeforePrint(object sender, EventArgs e)
{
//decide where the bottom border should be draw to
if (m_actions != null && m_actions.ShouldShowBottBorder)
{
subReport3.Border.BottomStyle = BorderLineStyle.ThickSolid;
subReport2.Border.BottomStyle = BorderLineStyle.Solid;
}
else if (m_causes != null && m_causes.ShouldShowBottBorder)
{
subReport2.Border.BottomStyle = BorderLineStyle.ThickSolid;
}
else
{
subReport1.Border.BottomStyle = BorderLineStyle.ThickSolid;
}
}
the issue is that every time I step through the eh_BeforePrint method, the values always equate to false even though I step through the sub reports and the values are properly set. What is happening to cause the bool property to reset to false?
Just changing it if there are any records to print in the Fetch_Data method of each sub report.
private void Causes_FetchData(object sender, FetchEventArgs eArgs)
{
if (m_pos < m_corrs.Count)
{
if (!ShouldShowBottBorder)
ShouldShowBottBorder = true;
//...
}
}

You cannot be assured that the BeforePrint event raises exactly after the corresponding FetchData event. For example, FetchData may fire many times for several records, but due to some keep together logic in the layout engine, it may take several records before ActiveReports knows which page it will commit a section to. Therefore, it is pretty common for FetchData to be raised for several events before the corresponding BeforePrint events are raised.
If I understand your code properly there is a bigger problem though. It appears you are calculating values in your subreports (m_causes and m_actions appear to be actual subreports). If that is the case you cannot reliably calculate values in your subreports and pass them out to the parent report. Instead, you'll need to calculate those values in your parent report. However, usually you can add some shared function to calculate the value and call it from the parent report, and then pass that value into the subreports.
Comment here with some more information if you have specific questions about doing that.
On an unrelated note, you can get a pretty significant performance boost if you change the way you're initializing your subreports. Always initialize your subreports in the ReportStart event and then set their data in the format event of the section containing the Subreport control. This way you initialize each subreport once instead of initializing each subureport for every record. For example:
private void so_ReportStart()
{
subreport1.Report = new SectInfo();
subreport2.Report = new Causes();
subreport3.Report = new Actions();
}
private void Detail_Format()
{ // assuming Detail is the section containing your subreports:
((SectInfo)subreport1.Report).SetParameters(Fields["sectName"].Value, Fields["sectTxt"].Value);
((Causes)subreport2.Report).SetParameters(Fields["compResID"].Value);
((Actions)subreport3.Report).SetParameters(Fields["compResID"].Value);
}
You would setup those "Fields" values in FetchData similar to how your initializing the subreports now. Something like the following:
private void so_FetchData(object sender, FetchEventArgs eArgs)
{
if (m_so != null && m_so.Rows.Count > (m_soRowCount + 1))
{
DataRow soDr = m_so.Rows[m_soRowCount++];
if (soDr != null)
{
var compResID = (int) soDr["CompResID"];
var result = (ComplianceLevel) soDr["Result"];
var sectNum = (int) soDr["JobSectType"];
var sectName = soDr["S" + sectNum + "Name"] as string;
var sectTxt = soDr["S" + sectNum + "Text"] as string;
Fields["CompLev"].Value = (result == ComplianceLevel.OtherThanSerious) ? "Other Than Serious" : result.ToString();
/** BEGIN NEW CODE **/
Fields["sectName"].Value = sectName;
Fields["sectTxt"].Value = sectTxt;
Fields["compResID"].Value = compResId;
/** END NEW CODE **/
/** OLD CODE:
m_sectInfo = new SectInfo(sectName, sectTxt);
m_causes = new Causes(compResID);
m_actions = new Actions(compResID);
subReport1.Report = m_sectInfo;
subReport2.Report = m_causes;
subReport3.Report = m_actions;
**/
eArgs.EOF = false;
}
}
else
{
eArgs.EOF = true;
}
}
To learn more about the events in ActiveReports see the Report Events concepts topic in the ActiveReports Online Help.
To learn more about passing data into Subreports see Subreports with Run-Time Data Sources in the ActiveReports Online Help.
Scott Willeke
GrapeCity inc.

Listbox clears all items during datasource change

When I change the datasource of my Listbox all items are cleared, when loading new data into this Listbox it stays clear.
I have another ListBox right new to this one with the same refresh code but that one refreshes perfectly.
private void RefreshContacts()
{
this.ListContacts.DataSource = null;
this.ListContacts.DataSource = this.contacts;
this.BoxCountContacts.Text = this.ListContacts.Items.Count.ToString();
}
Anyone have an idea how to fix the listbox from being cleared and bugged?
Here is the full refresh codes of the two listboxes
private Contact[] contacts, feed; private Boolean isFeed;
internal ArcFeed()
{
this.InitializeComponent();
this.contacts = this.feed = new Contact[0];
}
private void RefreshForm(Boolean isFeed)
{
if (isFeed)
{
this.RefreshFeed();
}
else
{
this.RefreshContacts();
}
}
private void RefreshContacts()
{
this.ListContacts.DataSource = null;
this.ListContacts.DataSource = this.contacts;
this.BoxCountContacts.Text = this.ListContacts.Items.Count.ToString();
}
private void RefreshFeed()
{
this.ListFeed.DataSource = null;
this.ListFeed.DataSource = this.feed;
this.BoxCountFeed.Text = this.ListFeed.Items.Count.ToString();
}
private void OpenFile()
{
if (this.isFeed)
{
this.BoxFileFeed.Text = this.DialogOpen.FileName;
this.feed = ArcBuzz.Load(this.DialogOpen.FileName);
}
else
{
this.BoxFileContacts.Text = this.DialogOpen.FileName;
this.contacts = ArcBuzz.Load(this.DialogOpen.FileName);
}
this.RefreshForm(this.isFeed);
}
All code is debugged and follows it's course properly, I don't see any errors, the correct listbox's datasource are set and changed.

Just to make sure, have you checked that there are actually items in the contacts collection?
Also, if you've got two Listboxes, double check that you are using the right Listbox in each of the refresh code sections.
Sounds stupid, but its silly mistakes like this that get overlooked a lot of the time. With databinding its usually something small like this stopping it working.

Datagridview causing IndexOutOfRangeException when clicked upon

I have a datagridview which we will call dataGridViewExample.
My object (the uncommon datatypes is because my database is SQLite):
class MyObject
{
public Int64 Vnr { get; set; }
public string Name { get; set; }
public Single Price { get; set; }
public int Amount { get; set; }
}
Here is the relevant code:
//This form gets called with a .ShowDialog(); in my form1.
private List<MyObjecte> ExampleList = new List<MyObject>();
public MyForm()
{
dataGridViewExample.DataSource = OrdreInkøbsListe;
}
private void AddtoDataGridViewExample()
{
//Add a new MyObject to the list
ExampleList.Add(new myObject()
{
Vnr = newVnr,
Amount = newAmount,
Price = newPrice,
Name = newName
});
//refresh datasource
dataGridViewExample.DataSource = null;
dataGridViewExample.Refresh();
dataGridViewExample.DataSource = OrdreInkøbsListe;
ddataGridViewExample.Refresh();
}
When MyForm gets called with a .ShowDialog, it shows up fine and displays my DataGridView example just fine. As you can read from the code, the ExampleListis initially empty, so it just shows an empty datagridview with 4 columns: Vnr, Name, Price & Amount. If I click inside it etc. nothing happens - so everything is working as planned, so far.
Everytime I call AddtoDataGridViewExample() it adds the new object to the Datagridview, and the datagridview does update, listing all the objects added so far (they show themself as rows, again according to plan).
Now, remember that I just said that nothing happened if you clicked inside DataGridViewExample before I have called AddtoDataGridViewExample()?
Well, after having called AddtoDataGridViewExample() once or more, the program will crash if I click inside DataGridViewExample (for example: the users wants to select a row). It throws an IndexOutOfRangeException and talks about an -1 index.
It also throws the exception in the other form, on the line where I call MyForm with .ShowDialog();
I really am stuck on this, do you guys have any idea what is wrong??
My only clue is that I do believe the refresh of DataGridViewExample's datasource might be the cause of the problem.
Another important note: I have yet bound any events to my DataGridViewExample. So you can rule that idea out.
Here is all DataGridViewExample's properties:
this.dataGridViewExample.AllowUserToAddRows = false;
this.dataGridViewExample.AllowUserToDeleteRows = false;
this.dataGridViewExample.AllowUserToResizeColumns = false;
this.dataGridViewExample.AllowUserToResizeRows = false;
this.dataGridViewExample.AutoSizeColumnsMode = System.Windows.Forms.DataGridViewAutoSizeColumnsMode.Fill;
this.dataGridViewExample.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize;
this.dataGridViewExample.Location = new System.Drawing.Point(591, 53);
this.dataGridViewExample.MultiSelect = false;
this.dataGridViewExample.Name = "dataGridViewExample";
this.dataGridViewExample.ReadOnly = true;
this.dataGridViewExample.RowHeadersVisible = false;
this.dataGridViewExample.SelectionMode = System.Windows.Forms.DataGridViewSelectionMode.FullRowSelect;
this.dataGridViewExample.ShowEditingIcon = false;
this.dataGridViewExample.Size = new System.Drawing.Size(240, 150);
this.dataGridViewExample.TabIndex = 31;

I guess the click event tries to get the currently selected row and do something with it, while dataGridViewExample.DataSource = null; clears the datasource, and the currently selected row becomes null.
If you set the DataGridView.DataSource to the list, you don't need to reset it to null, refresh, and reset it to the list again (and refresh again) to see the changes. It will be enough to just refresh the DataGridView.
You can also just try using an BindingList<T> object instead of a List<T>, which will automatically notify your grid of its internal changes (Adding and removing elements), and there's also an INotifyPropertyChanged interface you can implement on your MyObject class, that will make every property change in an object show on the grid (For any changes made to the object in the code, and not through the grid itself).

Have you tried running the debugger and break when InedxOutOfRangeException is thrown to see where the exception is thrown?
Select Debug > Exceptions then there's a Find button on the dialog so you don't have to browse through all of the possibilities.

I had similar situation. I assigned generic list of certain object to DataGridView. Then I was setting null to DataSource and after that refresh. After that I assign list of objects to DataSource. While clicked on grid while runtime error occured IndexOutOfRange. My solution was to assign new empty list of my object to that grid and refresh and after changes on my working list I do assign to DataSource and call Refresh. Now, it is working without any crashes. Please look on my code before:
grid.DataSource = null;
grid.Refresh();
if(cases.Count() > 0)
{
grid.DataSource = cases;
grid.Refresh();
}
And now on my code after:
grid.DataSource = new List<MyCase>();
grid.Refresh();
//do something with cases
if(cases.Count() > 0)
{
grid.DataSource = cases;
grid.Refresh();
}