Questions on UI for WinForms Forum

1 answer

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Object of type 'System.DBNull' cannot be converted to type 'System.String'. When throwing an exception from property.

Hello,

I have two issues.

The first issue is that I'm binding a Model to RadGridView, and throwing an exception when a value is invalid, and when throwing an exception from a property and catching it with DataError, GridViewDataErrorEventArgs.Exception is not the exception that was thrown from the property, but I get Object of type 'System.DBNull' cannot be converted to type 'System.String'.

This only happens when the property is null or empty string.

FYI, I'm allowing incorrect values to be assigned and do the validation after assigning the value to the property, and this is what I want, because I want to give the user an opportunity to correct base on the original value they entered.

Another issue is that when drawing borders to indicate which cell has a problem, not all borders appear.

As you can see above, I'm missing the top border.

It happens to another theme and sometimes the right side border is missing.

How can I make it so that all the borders appear?

The below is the sample code that you can use to reproduce the errors.

To reproduce the first problem, edit the first cell, clear the value, and the property will throw a "Please enter category name." exception but the exception in RadGridView1_DataError is Object of type 'System.DBNull' cannot be converted to type 'System.String' not the exception thrwon from the property setter.

To reproduce the second problem, edit the first cell, enter any value that is longer than 5 characters and you will see the red border without the top border.

public partial class GridViewTestForm : Form
{
    public GridViewTestForm()
    {
        InitializeComponent();

        List<GridViewDataColumn> gridColumns = new List<GridViewDataColumn>();

        gridColumns.Add(new GridViewTextBoxColumn
        {
            DataType = typeof(string),
            TextAlignment = ContentAlignment.MiddleLeft,
            FieldName = nameof(ReportCategoryViewModel.CategoryName),
            HeaderText = "Category Name",
            AutoSizeMode = BestFitColumnMode.DisplayedCells,
        });

        gridColumns.Add(new GridViewTextBoxColumn
        {
            DataType = typeof(string),
            TextAlignment = ContentAlignment.MiddleLeft,
            FieldName = nameof(ReportCategoryViewModel.NumberOfReportsUsingCategory),
            HeaderText = "# Reports",
            ReadOnly = true,
            AutoSizeMode = BestFitColumnMode.DisplayedCells,
        });

        gridColumns.Add(new GridViewTextBoxColumn
        {
            DataType = typeof(string),
            TextAlignment = ContentAlignment.MiddleLeft,
            FieldName = nameof(ReportCategoryViewModel.Description),
            HeaderText = "Description",
        });

        // Add the columns to the grid
        radGridView1.MasterTemplate.Columns.AddRange(gridColumns);
        radGridView1.EnableSorting = true;
        radGridView1.MasterTemplate.AllowMultiColumnSorting = true;

        radGridView1.DataError += RadGridView1_DataError;
        radGridView1.CellValidating += RadGridView1_CellValidating;

        var viewModel = new ReportCategoryManagementViewModel();
        viewModel.LoadReportCategories();
        radGridView1.DataSource = viewModel.ReportCategories;
    }

    private void RadGridView1_CellValidating(object sender, CellValidatingEventArgs e)
    {
        radGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].ErrorText = string.Empty;
        radGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].Style.CustomizeBorder = false;
    }

    private void RadGridView1_DataError(object sender, GridViewDataErrorEventArgs e)
    {
        radGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].ErrorText = e.Exception.Message;
        radGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].Style.CustomizeBorder = true;
        radGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].Style.DrawBorder = true;
        radGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].Style.BorderWidth = 1;
        radGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].Style.BorderGradientStyle = Telerik.WinControls.GradientStyles.Solid;
        radGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].Style.BorderColor = Color.Red;
        e.Cancel = true;
    }
}
public class NotifyPropertyBase : INotifyPropertyChanged
{
    public bool IgnoreValidation { get; set; } = false;
    public event PropertyChangedEventHandler PropertyChanged;
    public virtual void OnPropertyChangedRaised([CallerMemberName] string propertyName = "")
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}
public class ReportCategoryManagementViewModel : NotifyPropertyBase
{
    private ObservableCollection<ReportCategoryViewModel> _reportCategories = null;
    public ObservableCollection<ReportCategoryViewModel> ReportCategories => _reportCategories;
    public event EventHandler<List<ReportCategoryViewModel>> ReportCategoriesLoaded;
    public bool _isBusy = false;
    public bool IsBusy { get => _isBusy; set { if (_isBusy != value) { _isBusy = value; OnPropertyChangedRaised(); } } }
    public ReportCategoryManagementViewModel()
    {

    }
    public void LoadReportCategories()
    {
        _reportCategories = new ObservableCollection<ReportCategoryViewModel>()
        {
            new ReportCategoryViewModel()
            {
                IgnoreValidation = true,
                CategoryName = "My category",
                NumberOfReportsUsingCategory = 2,
                Description = "my optional description for my category"
            }
        };
        foreach(var category in _reportCategories)
            category.IgnoreValidation = false;
    }
}
public class ReportCategoryViewModel : NotifyPropertyBase
{
    public EntityState State { get; private set; } = EntityState.Unchanged;
    private string _categoryName = string.Empty;
    public string CategoryName
    {
        get => _categoryName;
        set
        {
            if (_categoryName != value)
            {
                _categoryName = value;
                OnPropertyChangedRaised();
                if (!IgnoreValidation)
                {
                    if (!string.IsNullOrWhiteSpace(_categoryName))
                    {
                        if (_categoryName.Length > 5)
                            throw new Exception("Maximum character is 5.");
                    }
                    else
                    {
                        _categoryName = string.Empty;
                        throw new Exception("Please enter category name.");
                    }
                }
            }
        }
    }
    private int _numberOfReportsUsingCategory;
    public int NumberOfReportsUsingCategory { get => _numberOfReportsUsingCategory; set { if (_numberOfReportsUsingCategory != value) { _numberOfReportsUsingCategory = value; OnPropertyChangedRaised(); } } }
    private string _description;
    public string Description { get => _description; set { if (_description != value) { _description = value; OnPropertyChangedRaised(); } } }
}

GridView

answered on 17 May 2021

1 answer

141 views

Radtoggleswitch not rendering as designed

I am new to Telerik controls.

I have updated the design of a radtoggleswitch. This is how it looks in the VS designer . But when i run the application the look changes to . Cannot figure out why this is happening. Am i missing something here,

Buttons, RadioButton, CheckBox, etc

answered on 11 May 2021

2 answers

149 views

Custom Sorting a grid based on numerical values

Hello

I have a databound grid that has a column containings integer numerical values as per the following example:

5
3
-1
2
-1
1
4

and I wish to sort this grid following the following rule:
for ascending sort I wish to have:

1
2
3
4
5
-1
-1

and for descending sort:

5
4
3
2
1
-1
-1

In other words I wish to have the negativ values always at the end and the positiv values at the top in ascending or descending order.

I have looked at the custom sorting documentation but I do not understand how to set the e.sortresult property to achieve this sort behavior

Thanks in advance
Best Regards
Pierre-Jean

GridView

answered on 10 May 2021

2 answers

910 views

RadPageView appearance settings

In the included screenshot I see the white borders (or background color) on the sides indicated by the red arrows. How can I make these borders disappear?

In the screenshot it is also visible that on the right side a lighter colored area appears, this color is the same is the color used to highlight the selected radpageviewpage (in the screenshot RadPageViewPage8). How can I prevent this from happening? To clarify I included a second screenshot which shows how I would like to see it.

I'm using Telerik.WinControls, Version=2018.3.1016.40.

The code below shows a form with can be used to reproduce the page views shown above (without the images and no toolbar):

<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()>
Partial Class Form1
    Inherits System.Windows.Forms.Form

    'Form overrides dispose to clean up the component list.
    <System.Diagnostics.DebuggerNonUserCode()>
    Protected Overrides Sub Dispose(ByVal disposing As Boolean)
        Try
            If disposing AndAlso components IsNot Nothing Then
                components.Dispose()
            End If
        Finally
            MyBase.Dispose(disposing)
        End Try
    End Sub

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.  
    'Do not modify it using the code editor.
    <System.Diagnostics.DebuggerStepThrough()>
    Private Sub InitializeComponent()
        Me.RadPageView1 = New Telerik.WinControls.UI.RadPageView()
        Me.RadPageViewPage1 = New Telerik.WinControls.UI.RadPageViewPage()
        Me.RadPageView3 = New Telerik.WinControls.UI.RadPageView()
        Me.RadPageViewPage10 = New Telerik.WinControls.UI.RadPageViewPage()
        Me.RadPageViewPage11 = New Telerik.WinControls.UI.RadPageViewPage()
        Me.RadPageViewPage2 = New Telerik.WinControls.UI.RadPageViewPage()
        Me.RadPageView2 = New Telerik.WinControls.UI.RadPageView()
        Me.RadPageViewPage6 = New Telerik.WinControls.UI.RadPageViewPage()
        Me.RadPageViewPage7 = New Telerik.WinControls.UI.RadPageViewPage()
        CType(Me.RadPageView1, System.ComponentModel.ISupportInitialize).BeginInit()
        Me.RadPageView1.SuspendLayout()
        Me.RadPageViewPage1.SuspendLayout()
        CType(Me.RadPageView3, System.ComponentModel.ISupportInitialize).BeginInit()
        Me.RadPageView3.SuspendLayout()
        Me.RadPageViewPage2.SuspendLayout()
        CType(Me.RadPageView2, System.ComponentModel.ISupportInitialize).BeginInit()
        Me.RadPageView2.SuspendLayout()
        Me.SuspendLayout()
        '
        'RadPageView1
        '
        Me.RadPageView1.Controls.Add(Me.RadPageViewPage1)
        Me.RadPageView1.Controls.Add(Me.RadPageViewPage2)
        Me.RadPageView1.Dock = System.Windows.Forms.DockStyle.Left
        Me.RadPageView1.ItemSizeMode = CType((Telerik.WinControls.UI.PageViewItemSizeMode.EqualWidth Or Telerik.WinControls.UI.PageViewItemSizeMode.EqualHeight), Telerik.WinControls.UI.PageViewItemSizeMode)
        Me.RadPageView1.Location = New System.Drawing.Point(0, 0)
        Me.RadPageView1.Name = "RadPageView1"
        Me.RadPageView1.PageBackColor = System.Drawing.Color.Transparent
        Me.RadPageView1.SelectedPage = Me.RadPageViewPage1
        Me.RadPageView1.Size = New System.Drawing.Size(182, 571)
        Me.RadPageView1.TabIndex = 3
        Me.RadPageView1.ViewMode = Telerik.WinControls.UI.PageViewMode.Stack
        CType(Me.RadPageView1.GetChildAt(0), Telerik.WinControls.UI.RadPageViewStackElement).ItemSpacing = 1
        '
        'RadPageViewPage1
        '
        Me.RadPageViewPage1.BackColor = System.Drawing.Color.Maroon
        Me.RadPageViewPage1.Controls.Add(Me.RadPageView3)
        Me.RadPageViewPage1.ForeColor = System.Drawing.SystemColors.ActiveCaptionText
        Me.RadPageViewPage1.ImageAlignment = System.Drawing.ContentAlignment.TopCenter
        Me.RadPageViewPage1.ItemSize = New System.Drawing.SizeF(182.0!, 32.0!)
        Me.RadPageViewPage1.Location = New System.Drawing.Point(5, 29)
        Me.RadPageViewPage1.Name = "RadPageViewPage1"
        Me.RadPageViewPage1.Size = New System.Drawing.Size(172, 476)
        Me.RadPageViewPage1.Text = "RadPageViewPage1"
        Me.RadPageViewPage1.TextAlignment = System.Drawing.ContentAlignment.MiddleCenter
        Me.RadPageViewPage1.TextImageRelation = System.Windows.Forms.TextImageRelation.ImageAboveText
        '
        'RadPageView3
        '
        Me.RadPageView3.Controls.Add(Me.RadPageViewPage10)
        Me.RadPageView3.Controls.Add(Me.RadPageViewPage11)
        Me.RadPageView3.Dock = System.Windows.Forms.DockStyle.Fill
        Me.RadPageView3.Location = New System.Drawing.Point(0, 0)
        Me.RadPageView3.Name = "RadPageView3"
        Me.RadPageView3.PageBackColor = System.Drawing.Color.Transparent
        Me.RadPageView3.SelectedPage = Me.RadPageViewPage10
        Me.RadPageView3.Size = New System.Drawing.Size(172, 476)
        Me.RadPageView3.TabIndex = 0
        CType(Me.RadPageView3.GetChildAt(0), Telerik.WinControls.UI.RadPageViewStripElement).StripButtons = Telerik.WinControls.UI.StripViewButtons.None
        CType(Me.RadPageView3.GetChildAt(0), Telerik.WinControls.UI.RadPageViewStripElement).StripAlignment = Telerik.WinControls.UI.StripViewAlignment.Left
        CType(Me.RadPageView3.GetChildAt(0), Telerik.WinControls.UI.RadPageViewStripElement).ItemContentOrientation = Telerik.WinControls.UI.PageViewContentOrientation.Horizontal
        '
        'RadPageViewPage10
        '
        Me.RadPageViewPage10.ImageAlignment = System.Drawing.ContentAlignment.TopCenter
        Me.RadPageViewPage10.ItemSize = New System.Drawing.SizeF(121.0!, 28.0!)
        Me.RadPageViewPage10.Location = New System.Drawing.Point(130, 10)
        Me.RadPageViewPage10.Name = "RadPageViewPage10"
        Me.RadPageViewPage10.Size = New System.Drawing.Size(31, 455)
        Me.RadPageViewPage10.Text = "RadPageViewPage10"
        Me.RadPageViewPage10.TextAlignment = System.Drawing.ContentAlignment.MiddleCenter
        Me.RadPageViewPage10.TextImageRelation = System.Windows.Forms.TextImageRelation.ImageAboveText
        '
        'RadPageViewPage11
        '
        Me.RadPageViewPage11.ItemSize = New System.Drawing.SizeF(121.0!, 28.0!)
        Me.RadPageViewPage11.Location = New System.Drawing.Point(130, 10)
        Me.RadPageViewPage11.Name = "RadPageViewPage11"
        Me.RadPageViewPage11.Size = New System.Drawing.Size(0, 297)
        Me.RadPageViewPage11.Text = "RadPageViewPage11"
        '
        'RadPageViewPage2
        '
        Me.RadPageViewPage2.Controls.Add(Me.RadPageView2)
        Me.RadPageViewPage2.ImageAlignment = System.Drawing.ContentAlignment.TopCenter
        Me.RadPageViewPage2.ItemSize = New System.Drawing.SizeF(182.0!, 32.0!)
        Me.RadPageViewPage2.Location = New System.Drawing.Point(5, 29)
        Me.RadPageViewPage2.Name = "RadPageViewPage2"
        Me.RadPageViewPage2.Size = New System.Drawing.Size(172, 476)
        Me.RadPageViewPage2.Text = "RadPageViewPage2"
        Me.RadPageViewPage2.TextAlignment = System.Drawing.ContentAlignment.MiddleCenter
        Me.RadPageViewPage2.TextImageRelation = System.Windows.Forms.TextImageRelation.ImageAboveText
        '
        'RadPageView2
        '
        Me.RadPageView2.Controls.Add(Me.RadPageViewPage6)
        Me.RadPageView2.Controls.Add(Me.RadPageViewPage7)
        Me.RadPageView2.Dock = System.Windows.Forms.DockStyle.Fill
        Me.RadPageView2.Location = New System.Drawing.Point(0, 0)
        Me.RadPageView2.Name = "RadPageView2"
        Me.RadPageView2.SelectedPage = Me.RadPageViewPage6
        Me.RadPageView2.Size = New System.Drawing.Size(172, 476)
        Me.RadPageView2.TabIndex = 1
        CType(Me.RadPageView2.GetChildAt(0), Telerik.WinControls.UI.RadPageViewStripElement).StripButtons = Telerik.WinControls.UI.StripViewButtons.None
        CType(Me.RadPageView2.GetChildAt(0), Telerik.WinControls.UI.RadPageViewStripElement).StripAlignment = Telerik.WinControls.UI.StripViewAlignment.Left
        CType(Me.RadPageView2.GetChildAt(0), Telerik.WinControls.UI.RadPageViewStripElement).ItemContentOrientation = Telerik.WinControls.UI.PageViewContentOrientation.Horizontal
        '
        'RadPageViewPage6
        '
        Me.RadPageViewPage6.ImageAlignment = System.Drawing.ContentAlignment.TopCenter
        Me.RadPageViewPage6.Location = New System.Drawing.Point(124, 10)
        Me.RadPageViewPage6.Name = "RadPageViewPage6"
        Me.RadPageViewPage6.Size = New System.Drawing.Size(22, 245)
        Me.RadPageViewPage6.Text = "RadPageViewPage6"
        Me.RadPageViewPage6.TextAlignment = System.Drawing.ContentAlignment.MiddleCenter
        Me.RadPageViewPage6.TextImageRelation = System.Windows.Forms.TextImageRelation.ImageAboveText
        '
        'RadPageViewPage7
        '
        Me.RadPageViewPage7.ImageAlignment = System.Drawing.ContentAlignment.TopCenter
        Me.RadPageViewPage7.Location = New System.Drawing.Point(124, 10)
        Me.RadPageViewPage7.Name = "RadPageViewPage7"
        Me.RadPageViewPage7.Size = New System.Drawing.Size(26, 297)
        Me.RadPageViewPage7.Text = "RadPageViewPage7"
        Me.RadPageViewPage7.TextAlignment = System.Drawing.ContentAlignment.MiddleCenter
        Me.RadPageViewPage7.TextImageRelation = System.Windows.Forms.TextImageRelation.ImageAboveText
        '
        'Form1
        '
        Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
        Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
        Me.ClientSize = New System.Drawing.Size(869, 571)
        Me.Controls.Add(Me.RadPageView1)
        Me.Name = "Form1"
        Me.Text = "Form1"
        CType(Me.RadPageView1, System.ComponentModel.ISupportInitialize).EndInit()
        Me.RadPageView1.ResumeLayout(False)
        Me.RadPageViewPage1.ResumeLayout(False)
        CType(Me.RadPageView3, System.ComponentModel.ISupportInitialize).EndInit()
        Me.RadPageView3.ResumeLayout(False)
        Me.RadPageViewPage2.ResumeLayout(False)
        CType(Me.RadPageView2, System.ComponentModel.ISupportInitialize).EndInit()
        Me.RadPageView2.ResumeLayout(False)
        Me.ResumeLayout(False)

    End Sub
    Friend WithEvents RadPageView1 As Telerik.WinControls.UI.RadPageView
    Friend WithEvents RadPageViewPage1 As Telerik.WinControls.UI.RadPageViewPage
    Friend WithEvents RadPageViewPage2 As Telerik.WinControls.UI.RadPageViewPage
    Friend WithEvents RadPageView2 As Telerik.WinControls.UI.RadPageView
    Friend WithEvents RadPageViewPage6 As Telerik.WinControls.UI.RadPageViewPage
    Friend WithEvents RadPageViewPage7 As Telerik.WinControls.UI.RadPageViewPage
    Friend WithEvents RadPageView3 As Telerik.WinControls.UI.RadPageView
    Friend WithEvents RadPageViewPage10 As Telerik.WinControls.UI.RadPageViewPage
    Friend WithEvents RadPageViewPage11 As Telerik.WinControls.UI.RadPageViewPage
End Class

PageView

answered on 10 May 2021

2 answers

220 views

Summary row item for editable checkbox column

Hi
I have RadGridView with editable checkbox column. I created custom summary row item which code i presented below.

public class CheckedRowsSummaryItem : GridViewSummaryItem

{

public CheckedRowsSummaryItem(string name, string formatString, GridAggregateFunction aggregate)

: base(name, formatString, aggregate)

{ }

public override object Evaluate(IHierarchicalRow row)

{

int count = 0;

foreach (GridViewRowInfo childRow in row.ChildRows)

{

try

{

if ((bool)childRow.Cells["chkBoxKol"].Value)

{

count++;

}

catch { }

}

return count;

}

My problem is that when I change the chceckbox state my custom row summary for the column is not refreshed until I change current row or current cell. I tried to set IsCurrent properity on false or rise EndEdit() method for the grid in CellBeginEdit event but these solutions not worked. How could I programmatically make my summary refresh to avoid changing current column by the user?

All the best

GridView

answered on 06 May 2021

8 answers

378 views

Trouble Resizing Radform with mouse

I have an issue where is can be difficult or impossible to resize the Radform using the mouse. The conditions;

Most recent Telerik controls at this time, OS is Win7 64 Ultimate
Style is Sizable, Minimum size is 1024,700
Only affects the top left and right corner
Happens on Win8 and VS2012 themes, but not the Office themes
The form height and width can always be adjusted from the top or sides of the form

What happens is when the mouse is moved into the corner and the diagonal resize cursor appears, the form will not resize. The attached image shows the effect.

In the first titlebar image, the mouse is moved into the corner from the center of the form. From the noted cursor position, the form cannot be resized. From this position, once a resize is attempted, repositioning the mouse and retrying the resize may not work at all.
In the second titlebar image, the mouse is moved in from outside the form, and from the noted cursor position resizing works fine.
In the third image with the Office theme there is never any problem.
The last 2 images show the same issue in the Telerik Theme viewer. The same scenario applies as noted in pt 1 & 2 above.

The issue is a problem since the average user does not know what is going on or why it won't resize. There is a lot of playing around with the mouse to get it work but it will not in many cases.

Form

answered on 06 May 2021

1 answer

160 views

override onkeydown in radmaskededitbox

Hi. I want to bring a custom control that inherits from RasMaskedEditBox. But onKeyDown and OnKeyPress events do not fired.

public class myMask: Radmaskededitbox

{

protected override void OnKeyDown(KeyEventArgs e)

{

//My codes

}

MaskedEditBox

answered on 05 May 2021

1 answer

524 views

How to change properties of radVirtualKeyboardForm?

Hello,

I would like to know if it is possible to access/change the same properties for the radVirtualKeyboardForm as it is possible for the radVirtualKeyboard. I'm creating an application for a touch screen and I would like to remove some buttons from the keyboard which are not related to the input the user has to enter.

If it is not possible: Is there a possibility to assign also a radVirtualKeyboard to a control? I mean, that the keyboard only appears, if the cursor focus is on the corresponding input field.

Thank you in advance and have a wonderful day!

VirtualKeyboard

answered on 05 May 2021

1 answer

128 views

Data Visualisation in RadMap Control

Hi,

I am curious to know whether there is out of box support for visualising GPX files on Radmap control. Any help / sample code will be appreciated.

Thanks in advance

Map

answered on 05 May 2021

1 answer

149 views

How to use Custom Font with BreadCrumbElement

Hello,

I have tried to use Custom Font with a BreadCrumb with the purpose of displaying an home icon for the first Element with the following code.

        MyBreadCrumb.BreadCrumbElement.Items(0).Text = ChrW(&HF015)
        MyBreadCrumb.BreadCrumbElement.Items(0).CustomFont = "Font Awesome 5 Free Solid"

But instead of a nice looking home Glyphs I have an old crossed ballot (see attached picture)

I'm missing something ?

By the way, you should take a look at Font Awesome Example (in VB.NET) in the following page https://docs.telerik.com/devtools/winforms/telerik-presentation-framework/glyphs and correct it. (the ChrW() instead of /uF017, the multiple variable settings instruction in one line).

Thank you for your support

Marco Guignard

BreadCrumb

answered on 05 May 2021