Why does my WPF TextBox not show any characters?

I have an application which includes a DLL written in WPF. This application starts with the login window (the appl开发者_运维技巧ication is a Windows Form and the DLL is in WPF). When I type the user name or password I can't see the characters in the textbox, but they are saved in the Text1 property of both the textBox or the passwordBox as expected.

What could explain this behavior, and how can I fix it so that I see the characters as they're typed?

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Maybe could it be the foreground color which is equal to the background color ? If you try selecting text after typing, do you get something ?

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the foreground and the background are not the same, i have checked it... i get the text i type in but i can't see it, this is the most weird thing i have ever seen....i have opened another project

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I have seen this in your scenario: when the WPF window is hosted from a Windows Form application.

You need to run the WPF window in a separate thread to avoid this problem.