column-types.md

TreeDataGrid column types

TreeDataGrid currently supports three different column types:

• TextColumn
• HierarchicalExpanderColumn
• TemplateColumn

TextColumn

TextColumn is useful when you want all cells in the column to have only text values. Usually, everything you need to instantiate TextColumn class is

new TextColumn<Person, string>("First Name", x => x.FirstName)

The first generic parameter here is your model type basically, the place where you want to grab data from. Person in this case. The second generic parameter here is the type of the property where you want to grab data from. In this case, it is a string, it will be used to know exactly which type your property has.

This is the signature of the TextColumn constructor. There are two most important parameters. The first one will be used to define the column header, usually, it would be a string. In the sample above it is "First Name". The second parameter is an expression to get the value of the property. In the sample above it is x => x.FirstName.

Note:
The sample above is taken from this article. If you feel like you need more examples feel free to check it, there is a sample that shows how to use TextColumns and how to run a whole TreeDataGrid using them.

CheckBoxColumn

As its name suggests, CheckBoxColumn displays a CheckBox in its cells. For a readonly checkbox:

new CheckColumn<Person>("Firstborn", x => x.IsFirstborn)

The first parameter defines the column header. The second parameter is an expression which gets the value of the property from the model.

For a read/write checkbox:

new CheckColumn<Person>("Firstborn", x => x.IsFirstborn, (o, v) => o.IsFirstborn = v)

This overload adds a second paramter which is the expression used to set the property in the model.

HierarchicalExpanderColumn

HierarchicalExpanderColumn can be used only with HierarchicalTreeDataGrid (a.k.a TreeView) thats what Hierarchical stands for in its name, also it can be used only with HierarchicalTreeDataGridSource. This type of columns can be useful when you want cells to show an expander to reveal nested data.

That's how you instantiate HierarchicalExpanderColumn class:

new HierarchicalExpanderColumn<Person>(new TextColumn<Person, string>("First Name", x => x.FirstName), x => x.Children)

HierarchicalExpanderColumn has only one generic parameter, it is your model type, same as in TextColumn, Person in this case.

Lets take a look at the HierarchicalExpanderColumn constructor.

The first parameter in the constructor is a nested column, you would usually want to display something besides the expander and that's why you need this parameter. In the sample above, we want to display text and we use TextColumn for that. The second parameter is a selector of the child elements, stuff that will be displayed when Expander is in the expanded state below the parent element.

Note:
The sample above is taken from this article. If you feel like you need more examples feel free to check it, there is a sample that shows how to use HierarchicalExpanderColumn and how to run a whole TreeDataGrid using it.

TemplateColumn

TemplateColumn is the most customizable way to create a column. Because cell contents are described by a data template, the options for how each cell is displayed is almost unlimited.

The TemplateColumn constructor takes the following parameters:

• header: The Column header
• cellTemplate: A data template which describes how cells in the column will be displayed
• cellEditingTemplate: A data template which describes how cells in the column will be displayed when in edit mode. If no cellEditingTemplate is provided, then edit mode will be disabled for the column.
• width: The width of the column
• options: Less frequently used options for the column

There are two overloads of the TemplateColumn constructor, which corresponds to the two ways in which a template can be specified:

1. Using a FuncDataTemplate to create a template in code:

new TemplateColumn<Person>(
    "Selected",
    new FuncDataTemplate<Person>((_, _) => new CheckBox
    {
        [!CheckBox.IsCheckedProperty] = new Binding("IsSelected"),
    }))

2. Using a template defined as a XAML resource:

<TreeDataGrid Name="fileViewer" Source="{Binding Files.Source}">
    <TreeDataGrid.Resources>
           
        <!-- Defines a named template for the column -->
        <DataTemplate x:Key="CheckBoxCell">
            <CheckBox IsChecked="{Binding IsSelected}"/>
        </DataTemplate>
        
    </DataTemplate>
              
    </TreeDataGrid.Resources>
</TreeDataGrid>

// CheckBoxCell is the key of the template defined in XAML.
new TemplateColumn<Person>("Selected", "CheckBoxCell");

TemplateColumn has only one generic parameter, it is your model type, the same as in TextColumn; Person in this case. The code above will create a column with header "Selected" and a CheckBox in each cell.