Develop Reference

Delete Multiple Items from ObservableCollection

I want to delete multiple items in an ObservableCollection in C#. My code is:
var item = (MoveDataModel)e.SelectedItem;
var answer = await DisplayAlert("Confirmation", "Are you sure you wish to delete " + item.value + "?", "Yes", "No");
if (answer)
{
var type = item.type;
var value = item.value;
foreach (var listItem in items)
{
if ((listItem.value == item.value) || (listItem.location == value && type == "Location"))
{
items.Remove(listItem);
itemCount--;
}
}
}
The first iteration works fine. However, it hangs on
foreach (var listItem in items)
on the second pass. I'm not sure how to make it work.

you can't modify a collection while you're iterating over it. Try something like this (I haven't checked the syntax, may need some cleanup)
var removeList = items.Where(x => x.value == value).Where(y => y.type = type).ToList();
foreach(var i in removeList) {
items.Remove(i);
itemCount--;
}

Have your own counter, cycle backwards through the list so you wont have to readjust for indexes you removed.
System.Collections.ObjectModel.ObservableCollection<object> list = new System.Collections.ObjectModel.ObservableCollection<object>();
private void RemoveStuff()
{
var i = list.Count - 1;
for (; i <= 0; i--)
{
// some checks here to make sure this is the time you really want to remove
list.Remove(i);
}
}

Write first and second column rows in listview inside each row in a text file

I'm using WinForms. In my form I have a listview and a button. When I click on the button the program writes all of the items in the listview into a text file. The problem is that I want the first and second column to be in one line.
Here is my code so far that i use to write to the text file:
using (StreamWriter sw = File.CreateText(DirectoryPath))
{
foreach (ListViewItem item in listView1.Items)
{
sw.WriteLine(item.Text);
for (int i = 1; i < item.SubItems.Count; i++)
{
sw.WriteLine(item.SubItems[i].Text);
}
}
}
My ListView
Problem output text file
How I want the text file to display

How about just
using (StreamWriter sw = File.CreateText(DirectoryPath))
{
foreach (ListViewItem item in listView1.Items)
{
sw.Write(item.Text + ": ");
for (int i = 1; i < item.SubItems.Count; i++)
{
sw.WriteLine(item.SubItems[i].Text);
}
}
}

It seems that your first cell "FirstPage" is the parent and all other items are sub items. Assuming you have only two columns below answer will work.
using (StreamWriter sw = File.CreateText(DirectoryPath))
{
foreach (ListViewItem item in listView1.Items)
{
sw.Write(string.Format("{0} :",item.Text));
for (int i = 1; i < item.SubItems.Count; i++)
{
if (i % 2 == 0)
{
sw.Write(string.Format("{0} :",item.SubItems[i].Text));
}
else
{
sw.WriteLine(item.SubItems[i].Text);
}
}
}
}
Alternative is; add each new row as a new item to the list view
string[] row = { "FirstPage", "$1.00" };
string[] row2 = { "SecondPage", "$1.00" };
var listViewItem = new ListViewItem(row);
listView1.Items.Add(listViewItem);
var listViewItem2 = new ListViewItem(row2);
listView1.Items.Add(listViewItem2);
and so on. You can iterate through a foreach loop for this adding and then use the below code which is flexible.
using (StreamWriter sw = File.CreateText(DirectoryPath))
{
foreach (ListViewItem item in listView1.Items)
{
sw.Write(string.Format("{0} :",item.Text));
for (int i = 1; i < item.SubItems.Count; i++)
{
sw.WriteLine(item.SubItems[i].Text);
}
}
}

You can do it in a more elegant way:
var str = listView1.Items.Cast<ListViewItem>()
.Select(x => x.SubItems.Cast<ListViewItem.ListViewSubItem>())
.Select(x => string.Join(":", x.Select(s => s.Text)));
System.IO.File.WriteAllLines(#"d:\file.txt", str);
Note: If you want to limit the columns for example save only first two columns, you can select sub items at second line this way: x.SubItems.Cast<ListViewItem.ListViewSubItem>().Take(2)

You should iterate the List View items, concatenate each one of the sub items into each other and then add the concatenated string to the text file at the end... I have adapted your code:
using (StreamWriter sw = File.CreateText(DirectoryPath))
{
foreach (ListViewItem item in listView1.Items)
{
string strText = "";
//I'm not sure why you start at 1 and not 0, anyway:
for (int i = 1; i < item.SubItems.Count; i++)
{
strText+= " " + item.SubItems[i].Text;
}
sw.WriteLine(strText);
}
}

Change text in multiple textboxes?

How would I go about making a for loop that changes the text in more than 1 textbox?
for (int i; i < 5; i++)
{
textbox(i).text = "something"
}
But I don't know how to get the I to represent the number after the textbox, does anyone know how to?

Store the textboxes in an Array and then loop over the array
for (int i; i < 5; i++)
{
textboxArray[i].text = "something"
}

You could use Controls.Find:
var txts = this.Controls.Find("textbox" + i, true); // true for recursive search
foreach(TextBox txt in txts)
txt.Text = "something";
or - if the TextBoxes are in the same container control(like the Form or a Panel)- with LINQ:
var txts = this.Controls.OfType<TextBox>().Where(txt => txt.Name == "textbox" + i);
foreach(TextBox txt in txts)
txt.Text = "something";
Actually you don't need the loop variable, you could also use String.StartsWith to get all:
var txts = this.Controls.OfType<TextBox>().Where(txt => txt.Name.StartsWith("textbox"));
foreach(TextBox txt in txts)
txt.Text = "something";

if you dont want to alter every textbox on your form just simply add them to a List:
List<TextBox> TextBoxes = new List<TextBox>();
TextBoxes.Add(This.TextBox1);
TextBoxes.Add(This.TextBox3):
then as others have suggested you could either linq or regular foreach the textboxes in the list
TextBoxes.Foreach(Textbox => TextBox.Text = "something");
or
foreach (TextBox r in TextBoxes)
{
r.Text = "something;
}

Clear contents of specific listview columns?

This is how I currently add info to my listview:
private void toolStripMenuItem2_Click(object sender, EventArgs e)
{
int totItems = Seq3.Count - 1;
if (PercentPopTolerance1.Count - 1 > totItems) totItems = PercentPopTolerance1.Count - 1;
for (int i = 0; i <= totItems; i++)
{
ListViewItem lvi = new ListViewItem();
string item1 = "";
string item2 = "";
if (Seq3.Count - 1 >= i) item1 = Seq3[i].ToString();
if (PercentPopTolerance1.Count - 1 >= i) item2 = PercentPopTolerance1[i].ToString();
lvi.SubItems.Add(item1);
lvi.SubItems.Add(item2);
listView2.Items.Add(lvi);
}
}
View of empty listview:
Now how would I clear the contents of any particular column? Say I want to add to column YYMM but before I do this, I want to clear that particular column. How would this be done?

You can clear column values like this
var items = listView1.Items;
foreach (ListViewItem item in items)
{
a.SubItems["YYWW"].Text = "";
}

You should specify a column by its name (a column corresponds to a subitem in a ListViewItem), note that this Name is not ColumnHeader.Name, I mean the corresponding ListViewSubItem.Name:
public void ClearColumn(string colName){
foreach(ListViewItem item in listView1.Items){
var cell = item.SubItems[colName];
if(cell != null) cell.Text = "";
}
}
The following code will work for ColumnHeader.Name passed in instead of ListViewSubItem.Name as the code above does:
public void ClearColumn(string columnHeaderName){
int i = listView1.Columns.IndexOfKey(columnHeaderName);
if(i == -1) return;
foreach(ListViewItem item in listView1.Items){
item.SubItems[i].Text = "";
}
}
You can try the following code to make it work for Text instead of Name:
public void ClearColumn(string colText){
if(listView1.Items.Count == 0) return;
var col = listView1.Columns.Cast<ColumnHeader>()
.Select((x,i)=>new{x,i})
.FirstOrDefault(a=>a.x.Text == colText);
if(col == null) return;
foreach(ListViewItem item in listView1.Items){
item.SubItems[col.i].Text = "";
}
}

How to cut, copy, paste any listview item in C#?

for (int i = 0; i < listView1.Items.Count; i++)
{
if (listView1.Items[i].Selected)
{
listView1.Items[i].Remove();
}
}
This function simply deletes the selected item in listview.. but i want to cut it and paste it somewhere else.

It sounds like you want to remove the selected listitems and move them to another listview.
ListView sourceListView = new ListView();
ListView destListView = new ListView();
var selected = sourceListView.Items
.Cast<ListViewItem>()
.Where(x => x.Selected)
.ToList();
foreach (var item in selected)
{
sourceListView.Items.Remove(item);
destListView.Items.Add(item);
}