How to allow only valid values in a combobox? [closed] - c#

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in C# with DotNet 4 i have a form with a combobox which is filled with values when starting the program.
Now user can dropdown and select one of the values.
But: It is also possible to write something new into the combobox-field.
Question: What can i do that it is NOT possible to write something which is not part of the list?
Thanks

To make the text portion of a ComboBox non-editable, set the DropDownStyle property to "DropDownList".

It can be done by simply assigning a property to combobox .DropDownStyle = ComboBoxStyle.DropDownList. but, this property do not allow to edit text. means you have to select item either by mouse or by up/down arrow key. You cannot filter result by selecting this property. if you wish to filter result but don't allow to accept invalid value then you can do this by writing some code in cmb_Validating event
private void cmb_Validating(object sender, CancelEventArgs e)
{
if (cmb.SelectedValue == null && cmb.Text != string.Empty)
e.Cancel=true;
}

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CS1525 C# Invalid expression term 'string' [closed]

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I have this error and I have no ideo about what should I do
The aim is when I click to button, it should read the word in textbox and save it into the string variable by its new factor.I have the error oin the topic
private void panel_button_kelimeekle_kaydet_Click(object sender, EventArgs e)
{
if(panel_checkbox_ing.Checked)
{
string (panel_textbox_kelimeekle_yab.Text) = Ingkelimeler[(Ingkelimeler.Length+1)];
}
}
If panel_textbox_kelimeekle_yab is already a textbox on your form, then you don't need to declare its type when you assign a value to it. C# thinks you're trying to declare a new string variable.
Change that line of code to
panel_textbox_kelimeekle_yab.Text = Ingkelimeler[(Ingkelimeler.Length+1)];
This probably won't solve all your problems, but at least it will get you on to the next error message. (You probably mean Length-1 in your array index, but there's really no way for us to know.)

Load More Items at End of ListView in Xamarin.Forms [closed]

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I am trying to add more items to at the End of The listview when scrolling, and while doing my research I found this link https://montemagno.com/load-more-items-at-end-of-listview-in/, But when I tried to apply it on my code, I got stuck. I just want to know if someone can help with this. thank you in advance
In my precise I also tried to use this listview that James Montemagno made available, but I did not succeed as well.
I then left for another listview with infinite scroll and it's working for me to this day.
https://github.com/CarlosHSantos/XamarinMarvelApp
I think there might be serveral Issues with your code:
You want your listViewJson.ItemsSource to be a ObservableCollection instead of a normal list. (I assume that it is a normal List, it is not obvious from the code your show)
You maybe want to implement the ItemAppearing in the following way:
ItemAppearing += async (sender, e) =>
if (isLoading || jokeDisplay.value.Count == 0)
return;
//hit bottom!
if (e.Item.ToString() == Items[Items.Count - 1])
{
await LoadItems();
}
};
Lastly, within LoadItems() function, you need to replace Items with
(listViewJson.ItemsSource as ObservableCollection<TypeOfTheItemHere>).Add(ItemToAddHere)
It would be easier if you would have a property within your JokeList class that holds the ObservableCollection, so that you don't have to do all the casting everytime you want to access it.

c# checklistbox check if item is selected [closed]

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It my sound trivial but I can't get around. How do I know if item in checklistbox is selected ? I've got checklistbox with 3 items and I'd like to do some 'if then' statements. Basically ,if chkbox1.Checked Items 'ABC' is selected / checked then..
Thanks
CheckedListBox contains CheckedItems property. You can get all checked items from this collection. Read here: MSDN
got this solved by using
GetItemCheckState(0) == CheckState.Checked
and using 0 first item ,1 second item etc.

how can I make my textbox capture characters why textbox does not capture input [closed]

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when I put a breakpoints on my textbox it shows textbox.length = "" even if there are characters in the textbox
There is no Length property present in TextBox Class.
Probably you mean to Check the Length on Textbox Text property which is of string type.
textbox.Text.Length
More info about the code would be nice. Is your Textbox really enabled? No transparent layer in front of it? You used the mySQL-Tag. Does that mean you use some kind of binding in textbox? Possibly you can't change the content of your textbox, because the database-binding / connection is read-only?
Is there really some textbox.length property?? Are you sure you are referring to the right property? Try this:
Convert.ToString(textBox1.TextLength)

Why does C# allow creating an object with the same reference? [closed]

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Here is an example of my code:
Button1_Click(object sender, EventArgs e)
{
PictureBox PB = new PictureBox;
PB.Name = TextBox1.Text;
}
In this code when a user clicks the button, a new object of type PictureBox will be created. Then Name will be assigned the object. How's this possible?
I mean if user clicks again, another object with same reference will be created. How's this possible?
How's this possible?
The Name property on a Control is just a string property - you can assign it anything you want, so having multiple controls with the same name is just the same as having multiple text boxes displaying the same text, or any other class with a string property.
Note that, in your case, you're not actually using or storing the PictureBox you create in any way, so it's going to be eligible for GC as soon as your method ends.

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