How to disable the selected item in the list

Question

I have a ListBox in my WinForms application and I want to disable some items in this list, for example, if I right-click on an item, it is disabled, and if I left a click on the disabled item, it must be enabled. How can i do this? Thank you very much

Answer 1

I have found a way. To do this, we must create our own ListBox control. :)

With it, you can enable or disable items with an index of goods.

 using System; using System.Collections.Generic; using System.Text; using System.Windows.Forms; using System.Drawing; using System.Collections; using System.ComponentModel; using System.Globalization; using System.Security; using System.Runtime.InteropServices; namespace Netdev.Windows.Forms { public class ListBox : System.Windows.Forms.ListBox { public event EventHandler<IndexEventArgs> DisabledItemSelected; protected virtual void OnDisabledItemSelected(object sender, IndexEventArgs e) { if (DisabledItemSelected != null) { DisabledItemSelected(sender, e); } } public ListBox() { DrawMode = System.Windows.Forms.DrawMode.OwnerDrawFixed; disabledIndices = new DisabledIndexCollection(this); } private int originalHeight = 0; private bool fontChanged = false; protected override void OnFontChanged(EventArgs e) { base.OnFontChanged(e); fontChanged = true; this.ItemHeight = FontHeight; this.Height = GetPreferredHeight(); fontChanged = false; } protected override void OnResize(EventArgs e) { base.OnResize(e); if (!fontChanged) this.originalHeight = this.Height; } public void DisableItem(int index) { disabledIndices.Add(index); } public void EnableItem(int index) { disabledIndices.Remove(index); } private int GetPreferredHeight() { if (!IntegralHeight) return this.Height; int currentHeight = this.originalHeight; int preferredHeight = PreferredHeight; if (currentHeight < preferredHeight) { // Calculate how many items currentheigh can hold. int number = currentHeight / ItemHeight; if (number < Items.Count) { preferredHeight = number * ItemHeight; int delta = currentHeight - preferredHeight; if (ItemHeight / 2 <= delta) { preferredHeight += ItemHeight; } preferredHeight += (SystemInformation.BorderSize.Height * 4) + 3; } else { preferredHeight = currentHeight; } } else preferredHeight = currentHeight; return preferredHeight; } protected override void OnSelectedIndexChanged(EventArgs e) { int currentSelectedIndex = SelectedIndex; List<int> selectedDisabledIndices = new List<int>(); for (int i = 0; i < SelectedIndices.Count; i++) { if (disabledIndices.Contains(SelectedIndices[i])) { selectedDisabledIndices.Add(SelectedIndices[i]); SelectedIndices.Remove(SelectedIndices[i]); } } foreach (int index in selectedDisabledIndices) { IndexEventArgs args = new IndexEventArgs(index); OnDisabledItemSelected(this, args); } if (currentSelectedIndex == SelectedIndex) base.OnSelectedIndexChanged(e); } protected override void OnDrawItem(System.Windows.Forms.DrawItemEventArgs e) { base.OnDrawItem(e); if (DesignMode && Items.Count == 0) { return; } if (e.Index != ListBox.NoMatches) { object item = this.Items[e.Index]; if (disabledIndices.Contains(e.Index)) { e.Graphics.FillRectangle(SystemBrushes.InactiveBorder, e.Bounds); if (item != null) { e.Graphics.DrawString(item.ToString(), e.Font, SystemBrushes.GrayText, e.Bounds); } } else { if (SelectionMode == System.Windows.Forms.SelectionMode.None) { e.Graphics.FillRectangle(SystemBrushes.Window, e.Bounds); if (item != null) { e.Graphics.DrawString(item.ToString(), e.Font, SystemBrushes.WindowText, e.Bounds); } } else { if ((e.State & DrawItemState.Selected) == DrawItemState.Selected) { e.Graphics.FillRectangle(SystemBrushes.Highlight, e.Bounds); e.DrawFocusRectangle(); if (item != null) { e.Graphics.DrawString(item.ToString(), e.Font, SystemBrushes.HighlightText, e.Bounds); } } else { e.Graphics.FillRectangle(SystemBrushes.Window, e.Bounds); if (item != null) { e.Graphics.DrawString(item.ToString(), e.Font, SystemBrushes.WindowText, e.Bounds); } } } } } } private DisabledIndexCollection disabledIndices; public DisabledIndexCollection DisabledIndices { get { return disabledIndices; } } public class DisabledIndexCollection : IList, ICollection, IEnumerable { // Fields private ListBox owner; private List<int> innerList = new List<int>(); // Methods public DisabledIndexCollection(ListBox owner) { this.owner = owner; } public void Add(int index) { if (((this.owner != null) && (this.owner.Items != null)) && ((index != -1) && !this.Contains(index))) { innerList.Add(index); this.owner.SetSelected(index, false); } } public void Clear() { if (this.owner != null) { innerList.Clear(); } } public bool Contains(int selectedIndex) { return (this.IndexOf(selectedIndex) != -1); } public void CopyTo(Array destination, int index) { int count = this.Count; for (int i = 0; i < count; i++) { destination.SetValue(this[i], (int)(i + index)); } } public IEnumerator GetEnumerator() { return new SelectedIndexEnumerator(this); } public int IndexOf(int selectedIndex) { if ((selectedIndex >= 0) && (selectedIndex < this.owner.Items.Count)) { for (int index = 0; index < innerList.Count; index++) { if (innerList[index] == selectedIndex) return index; } } return -1; } public void Remove(int index) { if (((this.owner != null) && (this.owner.Items != null)) && ((index != -1) && this.Contains(index))) { innerList.Remove(index); this.owner.SetSelected(index, false); } } int IList.Add(object value) { throw new NotSupportedException("ListBoxSelectedIndexCollectionIsReadOnly"); } void IList.Clear() { throw new NotSupportedException("ListBoxSelectedIndexCollectionIsReadOnly"); } bool IList.Contains(object selectedIndex) { return ((selectedIndex is int) && this.Contains((int)selectedIndex)); } int IList.IndexOf(object selectedIndex) { if (selectedIndex is int) { return this.IndexOf((int)selectedIndex); } return -1; } void IList.Insert(int index, object value) { throw new NotSupportedException("ListBoxSelectedIndexCollectionIsReadOnly"); } void IList.Remove(object value) { throw new NotSupportedException("ListBoxSelectedIndexCollectionIsReadOnly"); } void IList.RemoveAt(int index) { throw new NotSupportedException("ListBoxSelectedIndexCollectionIsReadOnly"); } // Properties [Browsable(false)] public int Count { get { return this.innerList.Count; } } public bool IsReadOnly { get { return true; } } public int this[int index] { get { return IndexOf(index); } } bool ICollection.IsSynchronized { get { return true; } } object ICollection.SyncRoot { get { return this; } } bool IList.IsFixedSize { get { return true; } } object IList.this[int index] { get { return this[index]; } set { throw new NotSupportedException("ListBoxSelectedIndexCollectionIsReadOnly"); } } // Nested Types private class SelectedIndexEnumerator : IEnumerator { // Fields private int current; private ListBox.DisabledIndexCollection items; // Methods public SelectedIndexEnumerator(ListBox.DisabledIndexCollection items) { this.items = items; this.current = -1; } bool IEnumerator.MoveNext() { if (this.current < (this.items.Count - 1)) { this.current++; return true; } this.current = this.items.Count; return false; } void IEnumerator.Reset() { this.current = -1; } // Properties object IEnumerator.Current { get { if ((this.current == -1) || (this.current == this.items.Count)) { throw new InvalidOperationException("ListEnumCurrentOutOfRange"); } return this.items[this.current]; } } } } public new void SetSelected(int index, bool value) { int num = (this.Items == null) ? 0 : this.Items.Count; if ((index < 0) || (index >= num)) { throw new ArgumentOutOfRangeException("index"); } if (this.SelectionMode == SelectionMode.None) { throw new InvalidOperationException("ListBoxInvalidSelectionMode"); } if (!disabledIndices.Contains(index)) { if (!value) { if (SelectedIndices.Contains(index)) SelectedIndices.Remove(index); } else { base.SetSelected(index, value); } } // Selected index deoes not change, however we should redraw the disabled item. else { if (!value) { // Remove selected item if it is in the list of selected indices. if (SelectedIndices.Contains(index)) SelectedIndices.Remove(index); } } Invalidate(GetItemRectangle(index)); } } public class IndexEventArgs : EventArgs { private int index; public int Index { get { return index; } set { index = value ; } } public IndexEventArgs(int index) { Index = index; } } } 

For use:

• Add a custom control to your tool box and drag the form.
• Use these methods in the list box listBox1.DisableItem(index); listBox1.EnableItem(index); listBox1.DisableItem(index); listBox1.EnableItem(index);
• Download it below.

Download source

Answer 2

The ListBox has no built-in Disable / Enable elements. However, you can do some tricks.

First you need to define your own class for the element that has the Enabled property.

Then you need to subscribe to the MouseDown event and check which button (righ or left) was pressed. And based on the position of x, y, get the element that was clicked. Then you set the Enabled property to True / False. The following are some examples:

Your own class

  public class Item { public Item() { // Enabled by default Enabled = true; } public bool Enabled { get; set; } public string Value { get; set; } public override string ToString() { return Value; } } 

MouseDown Event

 private void listBox1_MouseDown(object sender, MouseEventArgs e) { var item = (Item)listBox1.Items[listBox1.IndexFromPoint(eX, eY)]; if (e.Button == System.Windows.Forms.MouseButtons.Right) { item.Enabled = false; } else { item.Enabled = true; } } 

Answer 3

If for some reason the user control is not suitable, you can achieve the same result in terms of "visual" by dividing your results into two lists.

1st Control: ListBoxA (active).

2nd control: ListBoxB (inactive).

Add any items that are active / can be selected in ListBoxA and any items that need to be disabled for ListBoxB.

In the next section, note that the default item height for a standard ListBox is something like 18px.

Depending on the drawing mode of the controls / if you redefined this

You can control two controls vertically - dynamically setting the height of the first control to 18px times the number of elements in the ListBoxA

See an example below: ( https://snag.gy/4GHYiz.jpg )

Sure! This helps if you don't need disabled items to display in that order.