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Children element label NullReferenceException

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GridView

This is a migrated thread and some comments may be shown as answers.

Alan asked on 14 Apr 2009, 12:33 PM

An error occurs in the cellFormating event:

in the first databinding of gridview the error does not happen , but if I try a second databinding, for refresh the gridview,
the following error occurs:

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.NullReferenceException: Object reference not set to an instance of an object.
at Telerik.WinControls.Primitives.TextPrimitive.MeasureOverride(SizeF availableSize)

The code where the error occurs is the folowing:

    
             private void gvPremios_CellFormatting(object sender, CellFormattingEventArgs e)  
        
                                     {  
        
             if (e.CellElement.ColumnInfo is GridViewDataColumn && !(e.CellElement.RowElement is GridTableHeaderRowElement))  
        
                                         {  
        
                                                 GridViewDataColumn column = (GridViewDataColumn)e.CellElement.ColumnInfo;  
        
                                                 if (column.DataField == "MyColumn")  
        
                                                 {                         
        
                                                     if (e.CellElement.Children.Count > 0)  
        
                                                         return;  
        
                                                     RadLabelElement element = new RadLabelElement();  
        
                                                     element.Text = "<html>This is a test..."                                           
        
                                                    e.CellElement.Children.Add(element);  
        
                                                 }  
        
            }

The strange thing is in the "element.text" property, that if I not put the the tag "<html>"... the error does not happen, but, i need formating the field with a html code...
And the property "DisableHTMLRendering=false" is not working as it should, leaving the whole column unconfigured.

12 Answers, 1 is accepted

answered on 15 Apr 2009, 02:10 PM

Hi Alan,

You have opened two inquiries with the same question. Since support tickets get higher priority, we replied there first. The next day we noticed that you have the same question posted in the forums - this is why we replied to look into your support question.

We would also prefer to continue addressing this question in just one thread - this will make sure that we have all information in one place, rather than jumping back and forth between different threads. This will make us respond faster and more accurately.

Thank you for your understanding. We will reply in this thread shortly.

Kind regards,

Nikolay
the Telerik team

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answered on 15 Apr 2009, 04:26 PM

Hi Alan,

Here is an example of how I do it.

    
            //clear the gridview of everything 
        
            rgvNetwork.MasterGridViewTemplate.Columns.Clear(); 
        
            radGridView.MasterGridViewTemplate.Rows.Clear(); 
        
            radGridView.MasterGridViewTemplate.ChildGridViewTemplates.Clear(); 
        
            //add the columns for the master 
        
            radGridView.MasterGridViewTemplate.Columns.Add(new GridViewDataColumn { FieldName = "Id", HeaderText = "Name", HeaderTextAlignment = ContentAlignment.MiddleCenter }); 
        
            radGridView.MasterGridViewTemplate.Columns.Add(new GridViewDataColumn { FieldName = "Name", HeaderText = "Adserver Id", HeaderTextAlignment = ContentAlignment.MiddleCenter }); 
        
            radGridView.MasterGridViewTemplate.Columns.Add(new GridViewDataColumn { FieldName = "Active", HeaderText = "Active", HeaderTextAlignment = ContentAlignment.MiddleCenter }); 
        
            //add the columns for the childs 
        
            var template = new GridViewTemplate { AllowAddNewRow = false, AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill }; 
        
            template.Columns.Add(new GridViewTextBoxColumn { FieldName = "Id", IsVisible = false }); 
        
            template.Columns.Add(new GridViewTextBoxColumn { FieldName = "IdChild", HeaderText = "Zone Name", HeaderTextAlignment = ContentAlignment.MiddleCenter}); 
        
            template.Columns.Add(new GridViewTextBoxColumn { FieldName = "NameChild", HeaderText = "Zone Id", HeaderTextAlignment = ContentAlignment.MiddleCenter}); 
        
            //add the childtemplate to the master 
        
            radGridView.MasterGridViewTemplate.ChildGridViewTemplates.Add(template); 
        
            //make the relationship between master and child 
        
            var relation = new GridViewRelation(radGridView.MasterGridViewTemplate) 
        
                        { 
        
                            ChildTemplate = template, 
        
                            RelationName = "SiteZonesNetwork" 
        
                        }; 
        
            relation.ParentColumnNames.Add("Id"); //equals the fieldname 
        
            relation.ChildColumnNames.Add("Id"); //equals the fieldname 
        
            //add the relation 
        
            radGridView.Relations.Add(relation); 
        
            //load your List<Master> 
        
            var myListMaster = new List<Master>(); 
        
            var child1 = new List<Child>(); 
        
            child1.Add(new Child{ Id = 2, Name = "ChildTest2" }); 
        
            child1.Add(new Child{ Id = 3, Name = "ChildTest3" }); 
        
            var child2 = new List<Child>(); 
        
            child1.Add(new Child{ Id = 5, Name = "ChildTest5" }); 
        
            child1.Add(new Child{ Id = 6, Name = "ChildTest6" }); 
        
            child1.Add(new Child{ Id = 7, Name = "ChildTest7" }); 
        
            myListMaster.Add(new Master { Id = 1, Name = "Test", Childs = child1 }); 
        
            myListMaster.Add(new Master { Id = 4, Name = "Test2", Childs = child2 });                         
        
            //fill the radgridview 
        
            foreach(var myMaster in myListMaster){ 
        
              radGridView.MasterGridViewTemplate.Rows.Add(new object[] { myMaster.Id, myMaster.Name, myMaster.Active }); 
        
              template = radGridView.MasterGridViewTemplate.ChildGridViewTemplates[0]; 
        
              foreach(var child in myMaster.childs){ 
        
                template.Rows.Add(new object[] { myMaster.Id, child.Id, child.Name }); 
        
              } 
        
            }

Where my 2 objects are written like this:

    
            public class Master{ 
        
              public int Id {get;set;} 
        
              public string Name {get;set;} 
        
              public List<Child> Childs{get;set;} 
        
            } 
        
            public class Child{ 
        
              public int Id{get;set;} 
        
              public string Name {get;set;} 
        
            }

It's possible that I have typo's in the example code. I wrote it quickly in notepad. But I think you will get the idea.

	radgridview.MasterGridViewTemplate.Columns.Clear(); //clears the columns
	radgridview.MasterGridViewTemplate.Rows.Clear(); //clears the rows
	radgridview.MasterGridViewTemplate.ChildGridViewTemplates.Clear(); //clears the childs