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Resize Columns

The TreeList features two different column resizing mechanisms:

The example at the end of this page shows both options in action.

Resize by Dragging

The TreeList allows users to resize columns by dragging the borders between header cells.

To enable column resizing, set the Resizable parameter of the treelist to true.

To prevent the user from resizing a certain column, set its own parameter Resizable="false". The user will still be able to resize other columns around it.

Here a few notes on the resizing behavior:

  • If the column Width is less than MinResizableWidth and the user tries to resize the column, it will snap to its minimum width.
  • Similarly, if the column Width is greater than MaxResizableWidth, the column will snap to its maximum width.
  • In multi-column header scenarios, you may set MinResizableWidth or MaxResizableWidth to child columns only. Setting these attributes to parent columns will have no effect.

Autofit Columns

When column resizing is enabled, a double click on the resize handle between the header cells will automatically fit the column width to the content of the header, data and footers. This will remove text wrapping in the component.

The TreeList also exposes methods to programmatically resize columns to fit their contents:

  • AutoFitColumn(string id) - autofits the column with the specified Id attribute;
  • AutoFitColumns(IEnumerable<string> ids) - autofits multiple columns at once;
  • AutoFitAllColumns() - autofits all applicable columns (for example, this method does not affect the hierarchy expand/collapse column);

Autofitting specific columns preserves the current widths of all the other columns. Similar to column resizing, column autofitting can trigger a horizontal Grid scrollbar, or leave empty space after the last column.

Programmatic autofitting works even if column resizing is disabled.

Example

How column resizing works in the Telerik TreeList

TreeList Column Resizing and Autofitting

@* TreeList column resizing and autofitting *@
@* Drag the border between column headers to change the column width. You cannot resize the ID column itself. *@

<TelerikButton OnClick="@AutoFitSingleColumn">AutoFit Name Column</TelerikButton>
<TelerikButton OnClick="@AutoFitMultipleColumns">AutoFit Id and ParentId Columns</TelerikButton>
<TelerikButton OnClick="@AutoFitAllColumns">AutoFit All Columns</TelerikButton>

<TelerikTreeList @ref="@TreeList" Data="@Data" Resizable="true"
                 Pageable="true" IdField="Id" ParentIdField="ParentId" Width="650px" Height="400px">
    <TreeListColumns>
        <TreeListColumn Field="Name" Expandable="true" Width="320px" Id="NameColumn" />
        <TreeListColumn Field="Id" Resizable="false" Id="IdColumn" />
        <TreeListColumn Field="ParentId" Id="ParentIdColumn" />
        <TreeListColumn Field="HireDate" />
    </TreeListColumns>
</TelerikTreeList>

@code {
    public TelerikTreeList<Employee> TreeList { get; set; }
    public List<Employee> Data { get; set; }

    private void AutoFitSingleColumn()
    {
        TreeList.AutoFitColumn("NameColumn");
    }

    private void AutoFitMultipleColumns()
    {
        var columns = new List<string>() { "IdColumn", "ParentIdColumn" };
        TreeList.AutoFitColumns(columns);
    }

    private void AutoFitAllColumns()
    {
        TreeList.AutoFitAllColumns();
    }

    protected override async Task OnInitializedAsync()
    {
        Data = await GetTreeListData();
    }

    // sample models and data generation

    public class Employee
    {
        public int Id { get; set; }
        public int? ParentId { get; set; }
        public string Name { get; set; }
        public DateTime HireDate { get; set; }
    }

    async Task<List<Employee>> GetTreeListData()
    {
        List<Employee> data = new List<Employee>();

        for (int i = 1; i < 15; i++)
        {
            data.Add(new Employee
            {
                Id = i,
                ParentId = null,
                Name = $"root: {i}",
                HireDate = DateTime.Now.AddYears(-i)
            }); ;

            for (int j = 1; j < 4; j++)
            {
                int currId = i * 100 + j;
                data.Add(new Employee
                {
                    Id = currId,
                    ParentId = i,
                    Name = $"first level child {j} of {i}",
                    HireDate = DateTime.Now.AddDays(-currId)
                });

                for (int k = 1; k < 3; k++)
                {
                    int nestedId = currId * 1000 + k;
                    data.Add(new Employee
                    {
                        Id = nestedId,
                        ParentId = currId,
                        Name = $"second level child {k} of {i} and {currId}",
                        HireDate = DateTime.Now.AddMinutes(-nestedId)
                    }); ;
                }
            }
        }

        return await Task.FromResult(data);
    }
}

See Also

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