ClearTextButtonBehavior to acheive a better handling

[punker76]

sometimes the TextBoxHelper loaded methods for TextBox, PasswordBox and ComboBox doesn't work correct.

so this PR should fix this and should not a braking change :-D

Closes #1268

[punker76]

^^ @thoemmi @flagbug
/cc @JoeRobich @fuzzylee @arnoldpa @gilimak

[arnoldpa]

Works fine for me.

On short question: is the behavior wanted that after TextBoxHelper.ButtonCommand executed Control.Clear() get executed too?

[punker76]

@arnoldpa you have different scenarios (e.g. for a TextBox)

1. a MetroTextBox with ClearTextButton="True": it clears the text

<TextBox Controls:TextBoxHelper.ClearTextButton="True" />

2. a MetroTextBox with ClearTextButton="True" and button command: it fires the command and clears the text

<TextBox Controls:TextBoxHelper.ClearTextButton="True"
         Controls:TextBoxHelper.ButtonCommand="{Binding TextBoxButtonCmd, Mode=OneWay}" />

3. a SearchMetroTextBox or MetroButtonTextBox with ClearTextButton="True" and button command: it fires the command and clears the text

<TextBox Controls:TextBoxHelper.ClearTextButton="True"
         Controls:TextBoxHelper.ButtonCommand="{Binding TextBoxButtonCmd, Mode=OneWay}" />

4. a SearchMetroTextBox or MetroButtonTextBox with ClearTextButton="False" and button command: it fires only the command

<TextBox Controls:TextBoxHelper.ClearTextButton="False"
         Controls:TextBoxHelper.ButtonCommand="{Binding TextBoxButtonCmd, Mode=OneWay}" />

[arnoldpa]

thank you, now its clear for me :)

[JobaDiniz]

Hi, how can I show the button in the textbox, but replace the clear command entirely?
I want only my command to be fired, that is, textbox text should not be cleared.