این کدی که نوشتم
<Window x:Class="WpfApplication1.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Simple Textbox by wpf" Height="300" Width="300" >
<Grid>
<TextBox>
<TextBox.Name>txtNum1</TextBox.Name>
<TextBox.HorizontalAlignment>Center</TextBox.HorizontalAlignment>
<TextBox.VerticalAlignment>Center</TextBox.VerticalAlignment>
<TextBox.Background>
<RadialGradientBrush>
<RadialGradientBrush.GradientStops>
<GradientStop Color="#b1a4fb" Offset="0"/>
<GradientStop Color="Lime" Offset=".5"/>
<GradientStop Color="#a30c85" Offset="1"/>
</RadialGradientBrush.GradientStops>
</RadialGradientBrush>
</TextBox.Background>
<TextBox.Foreground>White</TextBox.Foreground>
<TextBox.Text>this is sample TextBox</TextBox.Text>
</TextBox>
</Grid>
</Window>
خطای که میده
Cannot implicitly convert type 'System.Windows.Media.RadialGradientBrush' to 'System.Windows.Controls.TextBox'