dxe:TextEdit is losing focus after clicking on the control and is not possible to type [closed]

I have a <dxe:TextEdit/> control in my UserControl in WPF application. The TextEdit control has a template which is containing a TextBlock.

  <dxe:TextEdit Name="WaterMarkTextEdit"
                              NullText="Type something..."
                              EditValue=""
                              Style="{StaticResource TextEditStyle}"
                              MaxWidth="230" 
                              Margin="0,30"/>

   <Style x:Key="CustomTextBoxEditStyle" TargetType="TextBox"  
           BasedOn="{StaticResource {themes:TextEditThemeKey ResourceKey=TextStyle}}">
        <Style.Triggers>
            <DataTrigger Binding="{Binding IsKeyboardFocusWithin, RelativeSource={RelativeSource Self}}"  
                         Value="False">
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="TextBox">
                            <TextBlock Text="{TemplateBinding Text}"  
                                       Style="{StaticResource TextTrimmedStyle}"
                                       Margin="3,0,0,0"  
                                       VerticalAlignment="Center" 
                                       IsHitTestVisible="False"/>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </DataTrigger>
        </Style.Triggers>
    </Style>

<Style x:Key="TextEditStyle" TargetType="dxe:TextEdit">
    <Style.Resources>
        <Style TargetType="ToolTip" BasedOn="{StaticResource ToolTipStyle}"/>
    </Style.Resources>
    <Setter Property="FontStyle" Value="Italic"/>
    <Setter Property="FontWeight" Value="Normal"/>
    <Setter Property="FontSize" Value="{StaticResource GlobalNormalTextFontSize}"/>
    <Setter Property="FontFamily" Value="{StaticResource GlobalFontFamily}"/>
    <Setter Property="Foreground" Value="{StaticResource PrimaryBrush}" />
    <Setter Property="BorderBrush" Value="{StaticResource PrimaryBrush}"/>
    <Setter Property="VerticalContentAlignment" Value="Center"/>
    <Setter Property="ShowError" Value="False"/>
    <Setter Property="UseLayoutRounding" Value="True"/>
    <Setter Property="EditTemplate">
        <Setter.Value>
            <ControlTemplate>
                <TextBox x:Name="PART_Editor"  
               TextWrapping="NoWrap"  
               helpers:EditorMarginHelper.Margin="3,3,3,3,0,3,3,3"
               Style="{StaticResource CustomTextBoxEditStyle}"/>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

So when the TextEdit is not clicked/focused then it is in readonly mode for a purpose. And when focused then user can type in TextEdit. So, I am using IsKeyboardFocusWithin boolean property in the datatrigger in styling of the TextEdit. If the property value is false then TextEdit is in readonly mode otherwise in edit mode. But even I focus on the control it does not go in edit mode.

Somehow Keyboard focus is overwriting by any other control and focus moves away from the TextEdit. To focus forcefully, I have created an extra event so that it stays focused on TextEdit.

In usercontrol.xaml file:

 <dxe:TextEdit Name="WaterMarkTextEdit" 
                              NullText="Type something..."
                              EditValue="Text edit box with water mark and drop shadow"
                              Style="{StaticResource TextEditWithWaterMarkAndDropShadowStyle}"
                              IsKeyboardFocusWithinChanged="WaterMarkTextEdit_OnIsKeyboardFocusWithinChanged"
                              MaxWidth="230" 
                              Height="60"
                              Margin="0,30"/>

In usercontrol.xaml.cs file:

//-----------------------------------------------------------------------------------------
            /// <summary>
            /// The event handler to force the keyboard focus; because somehow focus is moving away
            /// and keyboard is losing it's focus for the current control
            /// </summary>
            private void WaterMarkTextEdit_OnIsKeyboardFocusWithinChanged(object sender, DependencyPropertyChangedEventArgs e)
            {
                if ((bool)e.NewValue)
                {
                    Dispatcher.BeginInvoke(DispatcherPriority.Input,
                        new Action(delegate () {
                            Keyboard.Focus(WaterMarkTextEdit); // Set Keyboard Focus
                        }));
                }
            }