Hi Telerik support team,
I’m strugling with the Winforms GridView GroupComparer and need some help with it. I’ve seen the topic below:
https://docs.telerik.com/devtools/winforms/controls/gridview/grouping/sorting-group-rows
In my case I’ve a generic comparer in which I want to evaluate which column needs some sorting changes. These are my unitColumns and I have a reference to its list at the moment I create the comparer.
this.radGridView1.MasterTemplate.GroupComparer = new CustomGroupComparer(list);
The problem I walk into is that Telerik creates new CustomGroupComparers by itself (I think for every group?). It also demands an empty constructor. This way I have no option to get to the list that I need.
Is there a workaround for this problem?? For this moment I defined a hardcoded List inside the customComparer but that’s not the way to program it.
It would be nice if the custom comparer was part of the GroupDescriptor.
Regards,
Daniel
3 Answers, 1 is accepted
Hello Daniel,
Thank you for writing us.
I have read your scenario but I think I will need to have a look at when the custom GroupComparer is set. Could it be possible to modify the attached project to mimic your scenario so that I can debug it and think of a suitable solution?
I am looking forward to your reply.
Regards,
Dinko | Tech Support Engineer
Progress Telerik
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Hi Dinko,
I was not able to edit your project due to reference issues. Here is the content of my simplified groupcomparer. My intention and the issue I run into should be clear..
public class CustomGroupComparer : IComparer<Group<GridViewRowInfo>>
{
private List<string> _unitColumns = new List<string>
{
{"Length"},
{"Sawlength"},
};
//public Func<string, bool> UnitColumnsContainsKey;
public int Compare(Group<GridViewRowInfo> x, Group<GridViewRowInfo> y)
{
if (x.GetType().Name != y.GetType().Name)
{
return x is DataItemGroup<GridViewRowInfo> ? 1 : -1;
}
var dataGroup = (DataGroup)x;
var columnName = dataGroup.GroupDescriptor.GroupNames.FirstOrDefault().PropertyName;
if (columnName != null && _unitColumns.Contains(columnName))
{
// grouped column exists
// do some custom work and custom compareTo..
// for ilustation now default..
return x.Key.ToString().CompareTo(y.Key.ToString());
}
else
{
// not part of the list.. default compare
return x.Key.ToString().CompareTo(y.Key.ToString());
}
}
}
So the issue is that I don't want the list _unitColumns in the comparer. Because I can't use a own constructor for the comparer, I can't pass through a reference to my list (which exists elsewhere).
Telerik demands a empty constructor which is used at instantiating the customComparer.
The question is: how can I get a reference to an object inside the groupComparer?? If it is possible to interrupt at the place where Telerik instantiates the customComparer, it could be solved easy by setting a property or even call a different constructor in which my list reference can be passed.
Regards,
Daniel
Hi Daniel,
Thank you for the additional code.
I see what you are trying to achieve here. Indeed, the group-comparer is instantiated with reflection, by calling the parameterless constructor. The engine in RadGridView does not know of the particular implementation of your custom group-comparеr so it cannot pass a parameter to match the signature of your constructor.
What I can suggest here is to create a static property inside your custom group compared. This way you could have access to your custom collection.
public class CustomGroupComparer : IComparer<Group<GridViewRowInfo>>
{
private static List<string> _unitColumns;
public static List<string> UnitColumns
{
get { return _unitColumns; }
set { _unitColumns = value; }
}
public int Compare(Group<GridViewRowInfo> x, Group<GridViewRowInfo> y)
{
if (x.GetType().Name != y.GetType().Name)
{
return x is DataItemGroup<GridViewRowInfo> ? 1 : -1;
}
var dataGroup = (DataGroup)x;
var columnName = dataGroup.GroupDescriptor.GroupNames.FirstOrDefault().PropertyName;
if (columnName != null && UnitColumns.Contains(columnName))
{
// grouped column exists
// do some custom work and custom compareTo..
// for ilustation now default..
return x.Key.ToString().CompareTo(y.Key.ToString());
}
else
{
// not part of the list.. default compare
return x.Key.ToString().CompareTo(y.Key.ToString());
}
}
}CustomGroupComparer.UnitColumns = new List<string>
{
{"Length"},
{"Sawlength"},
};
this.radGridView1.MasterTemplate.GroupComparer = new CustomGroupComparer();I hope that this approach will work for you.
Regards,
Dinko | Tech Support Engineer
Progress Telerik
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