At least one object must implement icomparable

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Get an exception

At least one object must implement IComparable

plotter.Children.OfType<linegraph>().Where(x => x.Description.ToString() == (sender as CheckBox).Content.ToString()).Max();

What I have tried:

var lineToRemove = ((sender as CheckBox).ToolTip == null) ?
plotter.Children.OfType<linegraph>().Where(x => x.Description.ToString() == (sender as CheckBox).Content.ToString()).Max() :
plotter.Children.OfType<linegraph>().Where(x => x.Description.ToString() == (sender as CheckBox).Content.ToString() + " | " + (sender as CheckBox).ToolTip.ToString()).Max();

if (lineToRemove != null)
{
int a = plotter.Children.IndexOf(lineToRemove);
plotter.Children.Remove(lineToRemove);
plotter.Children.RemoveAt(a++);
}

Posted 10-Oct-19 22:53pm

Member 12237141

Updated 11-Oct-19 7:55am

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OriginalGriff · Accepted Answer · 2019-10-10T23:22:00

Check your linegraph type, and also make very sure you have the right line.

You get that error when trying to order a collection of objects that doesn't support IComparable, normally when you try to OrderBy them - I've not seen it for Max, but I guess it may be possible.
Certainly, when I try to get close to your code (and without your actuall classes I can't get that close) I get no problems:

C#

private class MyClass {
    public string Desc { get; set; }
    public MyClass(string s) { Desc = s; }
    }
private void FrmMain_Shown(object sender, EventArgs e)
    {
    List<MyClass> items = new List<MyClass>() { new MyClass("one"), new MyClass("two"), new MyClass("three") };
    MyClass y = items.Where(x => x.Desc.ToString() == "two".ToString()).Max();
    }

Richard Deeming · Accepted Answer · 2019-10-11T07:56:00

There are multiple matching items in the sequence, and your linegraph type doesn't implement IComparable, so there is no way for the Max method to know which item is "biggest".

Perhaps you meant to use the FirstOrDefault method instead?

C#

var lineToRemove = ((sender as CheckBox).ToolTip == null) 
    ? plotter.Children.OfType<linegraph>().FirstOrDefault(x => x.Description.ToString() == (sender as CheckBox).Content.ToString()) 
    : plotter.Children.OfType<linegraph>().FirstOrDefault(x => x.Description.ToString() == (sender as CheckBox).Content.ToString() + " | " + (sender as CheckBox).ToolTip.ToString());

Also note that sender as CheckBox can return null if the sender is not actually a CheckBox. That will lead to a NullReferenceException. If you're certain that the sender is always a CheckBox, use a cast instead.

C#

var checkBox = (CheckBox)sender;

string valueToMatch = checkBox.ToolTip is null
    ? checkBox.Content.ToString()
    : string.Format("{0} | {1}", checkBox.Content, checkBox.ToolTip);

var lineToRemove = plotter.Children.OfType<linegraph>().FirstOrDefault(x => x.Description == valueToMatch);

At least one object must implement icomparable

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