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If it's always the same Form, just cache it, and hide/reshow/bring to front as apropiate. The problem is you are creating always a new Form (via reflection), this is also not very "fast" so caching the "frm" variable has another advantage (just make it a member and initialize if null).
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johannesnestler wrote: The problem is you are creating always a new Form (via reflection), this is also not very "fast" so caching the "frm" variable has another advantage
I'd like to point out that reflection is not "slow". Creating a form is always an expensive operation, even if you call the constructor directly.
Bastard Programmer from Hell 
If you can't read my code, try converting it here[^]
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yes, that's a good and valid point, in this case the "impact" by reflecting the type is neglectible. Thank you for pointing that out.
But what luck for me, that my advice isn't totally wrong - and in general it's always a good habit to do "maximum caching of type information" when reflecting...
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You can do this without using Reflection; you can use Activator.CreateInstance:
Form newForm = (Form) Activator.CreateInstance(Type.GetType(YourNameSpace + "." + YourNewFormName)); Keep in mind that when you create a new Form of some specific Type, like a new "Form4," and cast it to the generic Type 'Form: the new Form has an empty string for its 'Name property. So, you can't test if the new Form exists in the Application.OpenForms collection by using its Name. To fix that: give the new Form a Name when you create it:
Form newForm = (Form) Activator.CreateInstance(Type.GetType(YourNameSpace + "." + YourNewFormName));
newForm.Owner = this;
newForm.Name = YourNewFormName;
newForm.Show(); I'd like to suggest you define your own List<string> of currently opened secondary Form names; it will simplify testing for an instance being already opened. You can also pre-define a string with your NameSpace plus "." to make creating a new Form simpler.
“The best hope is that one of these days the Ground will get disgusted enough just to walk away ~ leaving people with nothing more to stand ON than what they have so bloody well stood FOR up to now.” Kenneth Patchen, Poet
modified 24-Feb-14 12:51pm.
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Looking at your code, the problem appears to be with the frm.Focus(); line:
- You create a new instance of the form type;
- You check to see if there is an open form of the same type;
- If there is, you call the
Focus method on the new form instance;
I suspect that calling Focus on an invisible form causes it to be shown.
Try something like this instead:
private Form FindOpenFormOfType(Type formType)
{
foreach (Form form in Application.OpenForms)
{
if (form.GetType() == formType)
{
return form;
}
}
return null;
}
private void klikMenu(object sender, EventArgs e)
{
string sFormName = "AIO_System." + ((ToolStripMenuItem)sender).Tag.ToString();
System.Reflection.Assembly asm = System.Reflection.Assembly.GetExecutingAssembly();
Type formType = asm.GetType(sFormName);
Form frm = FindOpenFormOfType(formType);
if (frm == null)
{
frm = (Form)Activator.CreateInstance(formType);
frm.Owner = this;
frm.Show();
}
else
{
frm.Focus();
}
}
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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Richard Deeming wrote: I suspect that calling Focus on an invisible form causes it to be shown.
In Windows Forms calling 'Focus on an instantiated, but hidden, Form will not cause it become visible.
Your code would work "as is" if you removed the modifier ".Tag" in the line where 'sFormName is constructed ... but, we can't know, from the information the OP presented, what they've done to create a 'Tag property for the ToolStripMenuItems ... that's not shown in the code posted here.
“The best hope is that one of these days the Ground will get disgusted enough just to walk away ~ leaving people with nothing more to stand ON than what they have so bloody well stood FOR up to now.” Kenneth Patchen, Poet
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if(frm != null)
{
MessageBox.Show("already running");
}
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I have added a new column to my database table. When I have added this new columnm, the first chance exception start appearing. When I debugged it, it stated the code line
MLongListSelector.ItemsSource = c.ToDoList.ToList(); is the next statement to execute that causes the problem. What have I done wrong there?
using (DatabaseContext c = new DatabaseContext(DatabaseContext.ConnectionString))
{
c.CreateIfNotExists();
c.LogDebug = true;
//output todolist data from database
MLongListSelector.ItemsSource = c.ToDoList.ToList();
}
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Check the column name and connection to database
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I have finally solved it . There was a problem in creating the database. instead of CreateIfNotExist() i used If(!DatabaseExist()){CreateDatabase();}
This solved it. It doesn't really make sense to me as it is actually the same thing. But it works.
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Hi Guys,
Ive just finished my admin panel that uses an SQL source and fills a list view with all clients and allows admins to update, edit Customer details..
Im trying to do the same thing for my User Panel (after user logs in and wants to edit their information)
Im using Context.User.Identity.Name(page_Load) in a label to welcome the user (can I SELECT the value from here??)
I don't want all the customer details coming up, just the ones for that particular user.
Is it possible to display only the customer information for the Current user? and again just in a simple listview
Any help is appreciated,
any questions, just ask.
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Unless I'm misunderstanding, would a simple WHERE clause allow you to limit the returned Customer details for just that customer whose username is Context.User.Identity.Name?
/ravi
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I'v inherited ComboBox in C#.net winform , and I'v drew a rectangle's diagonal(like 'X') behind the content of each item in the override method OnDrawItem . Now I want to implement a function, when mouse click the area of rectangle can delete current item , rather than to select the current item.
Anyone can help, Thank y:confusedou very much!
Denny Xue
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Unfortunately, that MSDN example code (all too typical of the so often valueless, poorly written, code samples on MSDN) does only one thing: it automatically removes all instances of ComboBoxItems with the same (string) value: an off-topic digression in terms of illustrating what the SelectedIndexChanged Event is about.
In the "real-world," you would filter your ComboBox Items in some way (via Linq 'Distinct if you were data binding, etc.) so you prevented duplicates. I suppose, in some exotic case one would allow duplicates, but I have yet to see that.
In this case, the OP wants to remove a ComboBoxItem only if the the end-user clicks on a special owner-drawn area of the ComboBoxItem. We don't know if the OP "allows" duplicate items, or wishes to remove duplicate ComboBoxItems.
Forgive me if I sound like I'm displacing anti-MSDN-doc-fervor ... onto you ... please 
“The best hope is that one of these days the Ground will get disgusted enough just to walk away ~ leaving people with nothing more to stand ON than what they have so bloody well stood FOR up to now.” Kenneth Patchen, Poet
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BillWoodruff wrote: all too typical of the so often valueless, poorly written, code samples on MSDN
You sir have not seen the "examples" and "documentation" put forth by Telerik and the Kendo UI library! That stuff makes Microsofts look absolutely awesome in comparison! No joke.
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Dave Kreskowiak wrote: not seen the "examples" and "documentation" put forth by Telerik and the Kendo UI library
Indeed, have not; I am grateful for such small blessings
“The best hope is that one of these days the Ground will get disgusted enough just to walk away ~ leaving people with nothing more to stand ON than what they have so bloody well stood FOR up to now.” Kenneth Patchen, Poet
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Dave Kreskowiak wrote: "documentation" put forth by Telerik and the Kendo UI library!
Don't know about Telerik but wholeheartedly agree about Kendo. One of the reasons we chose to not adopt that toolkit was the non-documentation.
/ravi
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What did you get in its place?
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We built our own framework on top of Dojo[^].
/ravi
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It's a starting point which would, I hope, but know all too often will not, help the OP to a) make better use of search engines and MSDN, and b) think for themselves.
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Thanks for you help! I'll find the solution. Sorry for reply later!
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I am sure you learned a lot implementing a custom ComboBoxItem using 'OnDrawItem. As you've found out, trying to access the hidden internal ListView that is displayed when the ComboBox drops its DropDown is problematic.
The only Event I've found that lets you determine the location of the mouse for any action in a ComboBox DropDown, without using WinAPI, is the SelectedIndexChanged Event. Consider:
private private Point hitPoint;
private int deleteThreshold = 100;
private void SomeComboBox_SelectedIndexChanged(object sender, EventArgs e)
{
hitPoint = SomeComboBox.PointToClient(MousePosition);
if(hitPoint.X > deleteThreshold) SomeComboBox.Items.Remove(SomeComboBox.SelectedItem);
}You could simplify this in a way that does not require 'OnDrawItem, however, the "sacrifice" would be that you would include the "X" as part of the Text of the ComboBoxItem itself, so the "X" could not appear in any special Font, not have any special formatting.
If you want to see an example of this, just let me know, and I'll post sample code here.
“The best hope is that one of these days the Ground will get disgusted enough just to walk away ~ leaving people with nothing more to stand ON than what they have so bloody well stood FOR up to now.” Kenneth Patchen, Poet
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Thanks for your help Sir. I'll try your suggestion. I like DIY, not just taking.
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Member 10413292 wrote: I like DIY, not just taking.
That's a great attitude; my best wishes for your success  Bill
“The best hope is that one of these days the Ground will get disgusted enough just to walk away ~ leaving people with nothing more to stand ON than what they have so bloody well stood FOR up to now.” Kenneth Patchen, Poet
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