How to dynamically change / set checkedListBox ite

问题:

I have code below. How can i set checkedListBox item fore colour depending on if item is checked or not checked?

private void FindSelectedUserRoles()
{
        lblSelectedUser.Text = Code.CommonUtilities.getDgvStringColValue(dataGridViewUserList, "UserName").Trim();

        //iterate all roles selected user is member of
        for (int i = 0; i < checkedListRoles.Items.Count; i++)
        {
            string roleName = checkedListRoles.Items[i].ToString();
            string selectedUserRoles = Code.MemberShipManager.GetSpecificUsersRoles(lblSelectedUser.Text.Trim());

            if (selectedUserRoles.Contains(roleName))
            {
                checkedListRoles.SetItemChecked(i, true);
                //here i want to set item fore colour to green

            }
            else if (selectedUserRoles.Contains(roleName) == false)
            {
                checkedListRoles.SetItemChecked(i, false);
                //and here, i want item fore colour to remain black
            }
        }
}

回答1:

I think you have to draw your own CheckedListBox item like this:

public class CustomCheckedListBox : CheckedListBox
{
    public CustomCheckedListBox()
    {
        DoubleBuffered = true;
    }
    protected override void OnDrawItem(DrawItemEventArgs e)
    {            
        Size checkSize = CheckBoxRenderer.GetGlyphSize(e.Graphics, System.Windows.Forms.VisualStyles.CheckBoxState.MixedNormal);
        int dx = (e.Bounds.Height - checkSize.Width)/2;
        e.DrawBackground();
        bool isChecked = GetItemChecked(e.Index);//For some reason e.State doesn't work so we have to do this instead.
        CheckBoxRenderer.DrawCheckBox(e.Graphics, new Point(dx, e.Bounds.Top + dx), isChecked ? System.Windows.Forms.VisualStyles.CheckBoxState.CheckedNormal : System.Windows.Forms.VisualStyles.CheckBoxState.UncheckedNormal);
        using (StringFormat sf = new StringFormat { LineAlignment = StringAlignment.Center })
        {
            using (Brush brush = new SolidBrush(isChecked ? CheckedItemColor : ForeColor))
            {
                e.Graphics.DrawString(Items[e.Index].ToString(), Font, brush, new Rectangle(e.Bounds.Height, e.Bounds.Top, e.Bounds.Width - e.Bounds.Height, e.Bounds.Height), sf);
            }
        }            
    }
    Color checkedItemColor = Color.Green;
    public Color CheckedItemColor
    {
        get { return checkedItemColor; }
        set
        {
            checkedItemColor = value;
            Invalidate();
        }
    }
}

If you want to set CheckedColor differently for each item, you have to store the CheckedColor setting for each item (such as in a Collection) and reference the CheckedColor using Index. However I think it's a little much work to do. So if you have such a requirement, going for ListView instead would be better.

回答2:

I think you should try ListView instead of checkedListBox. It has necessary properties and could be customized as you wish. Just set Checkboxes property to true, and then in your code add forecolor like that:

listView1.Items[i].ForeColor = Color.Red;

回答3:

Since it's rather complicated to draw the thing yourself, you could actually let the original control draw itself -- just tweaking the color. This is my suggestion:

public class CustomCheckedListBox : CheckedListBox
{
    protected override void OnDrawItem(DrawItemEventArgs e)
    {
        Color foreColor;
        if (e.Index >= 0)
        {
            foreColor = GetItemChecked(e.Index) ? Color.Green : Color.Red;
        }
        else
        {
            foreColor = e.ForeColor;
        }

        // Copy the original event args, just tweaking the fore color.
        var tweakedEventArgs = new DrawItemEventArgs(
            e.Graphics,
            e.Font,
            e.Bounds,
            e.Index,
            e.State,
            foreColor,
            e.BackColor);

        // Call the original OnDrawItem, but supply the tweaked color.
        base.OnDrawItem(tweakedEventArgs);
    }
}

回答4:

Expanding on @Mattias' answer, I made this custom control to fit my needs. I needed it to have colors depending on other factors than the Checked value.

public class CheckedListBoxColorable : CheckedListBox
{
    /// <summary>
    /// Controls the forecolors of the objects in the Items collection.
    /// If the item is not represented, it will have the default forecolor.
    /// </summary>
    public Dictionary<object, Color> Colors { get; set; }

    public CheckedListBoxColorable()
    {
        this.DoubleBuffered = true; //prevent flicker, not sure if this is necessary.
    }

    protected override void OnDrawItem(DrawItemEventArgs e)
    {
        //Default forecolor
        Color foreColor = e.ForeColor;

        //Item to be drawn
        object item = null;

        if (e.Index >= 0) //If index is -1, no customization is necessary
        {
            //Find the item to be drawn
            if (this.Items.Count > e.Index) item = this.Items[e.Index];

            //If the item was found and we have a color for it, get the custom forecolor
            if (item != null && this.Colors != null && this.Colors.ContainsKey(item))
            {
                foreColor = this.Colors[item];
            }
        }

        // Copy the original event args, just tweaking the forecolor.
        var tweakedEventArgs = new DrawItemEventArgs(
            e.Graphics,
            e.Font,
            e.Bounds,
            e.Index,
            e.State,
            foreColor,
            e.BackColor);

        // Call the original OnDrawItem, but supply the tweaked color.
        base.OnDrawItem(tweakedEventArgs);
    }
}

Usage:

//Set the colors I want for my objects
foreach (var obj in objects)
{
    //Add your own logic here to set the color depending on whatever criteria you have
    if (obj.SomeProperty) lstBoxes.Colors.Add(obj, Color.Green);
    else lstBoxes.Colors.Add(obj, Color.Red);
}
//Add the items to the checkedlistbox
lstBoxes.Items.AddRange(objects.ToArray());

回答5:

The accepted answer worked for me but it needs modifying if you want to disable the CustomCheckedListBox.

I modified the code as follows: -

I changed the 'CheckBoxRenderer.DrawCheckBox...' line to

if(Enabled)
{
    CheckBoxRenderer.DrawCheckBox(e.Graphics, new Point(dx, e.Bounds.Top + dx), isChecked ? System.Windows.Forms.VisualStyles.CheckBoxState.CheckedNormal : System.Windows.Forms.VisualStyles.CheckBoxState.UncheckedNormal);
}
else
{
    CheckBoxRenderer.DrawCheckBox(e.Graphics, new Point(dx, e.Bounds.Top + dx), isChecked ? System.Windows.Forms.VisualStyles.CheckBoxState.CheckedDisabled : System.Windows.Forms.VisualStyles.CheckBoxState.UncheckedDisabled);
}

and then I changed the 'using (Brush brush = new SolidBrush...' line to

using (Brush brush = new SolidBrush(isChecked ? CheckedItemColor : (Enabled ? ForeColor : SystemColors.GrayText)))

This caused enabling/disabling to work for me.