mateo/mateo/First.xaml

<Window x:Class="mateo.First"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:mateo"
        mc:Ignorable="d"
        Title="First" Height="450" Width="800" WindowStartupLocation="CenterScreen" ResizeMode="NoResize" WindowStyle="None" AllowsTransparency="True" Background="Transparent">
    <Grid Background="White">
        <Button x:Name="exit" Height="40" Width="40" Background="Transparent" BorderThickness="0" Click="btn_exit" Margin="750,10,10,400">
            <Image Source="image\exit.png" Height="40" Width="40"/>
        </Button>

        <Grid  Background="#E74C32" Margin="0,0,405,-0.4">
            <Image Source="image/logo.png" Margin="44,247,77,0"/>
        </Grid>

        <Grid x:Name="grid_vhod" Margin="400,0,0,-0.4" Visibility="Visible">
            <TextBlock Text="Авторизация" FontSize="24" FontFamily="Century Gothic" HorizontalAlignment="Center" Margin="114,66,110,345"/>

            <TextBlock x:Name="txtlogin" Text="Логин" FontFamily="Century Gothic" FontSize="18" Foreground="Gray" Margin="64,162,63,259"/>
            <TextBox TextChanged="txtchangedLogin" Background="Transparent" x:Name="vvod_login" FontSize="18" FontFamily="Century Gothic"
                 BorderThickness="0 0 0 2" BorderBrush="Black" MaxLength="20" Margin="64,162,63,259" PreviewTextInput="txtPasswordLogin_PreviewTextInput"/>

            <TextBlock x:Name="txtpass" Text="Пароль" FontSize="18" FontFamily="Century Gothic" Foreground="Gray" Margin="64,226,63,198"/>
            <PasswordBox PasswordChanged="passchangedPass" x:Name="vvod_pass" FontSize="18" Background="Transparent"
                     BorderThickness="0 0 0 2" BorderBrush="Black" MaxLength="20" Margin="64,226,63,198" PreviewTextInput="txtPasswordLogin_PreviewTextInput"/>

            <Button x:Name="vhod" Content="Войти" Background="Black" Foreground="White" FontSize="18" FontFamily="Century Gothic" Click="btn_vhod" Margin="123,293,123,104" IsDefault="True"/>
            <Button x:Name="registr" Content="Нет аккаунта? Зарегистрироваться" Background="Transparent" FontSize="18" FontFamily="Century Gothic" BorderThickness="0" Click="btn_registr" Margin="40,351,40,70"/>
        </Grid>

        <Grid x:Name="grid_registr" Margin="400,0,0,-0.4" Visibility="Hidden">
            <!--<Grid.ColumnDefinitions>
                <ColumnDefinition Width="0*"/>
                <ColumnDefinition/>
            </Grid.ColumnDefinitions>-->

            <Button x:Name="cancel" Content="←" FontSize="40" FontFamily="Century Gothic" Width="40" Background="Transparent" BorderThickness="0" Click="btnCancel" Margin="0,0,360,396"/>
            <TextBlock Text="Регистрация" FontSize="24" FontFamily="Century Gothic" HorizontalAlignment="Center" Margin="101,10,102,396"/>
            
            <TextBlock x:Name="txtlastreg" Text="Фамилия" FontSize="18" FontFamily="Century Gothic" Foreground="Gray" Margin="64,90,63,330" Grid.ColumnSpan="2" />
            <TextBox TextChanged="txtchangedLogin" x:Name="vvod_LNAME" FontSize="18" FontFamily="Century Gothic" Background="Transparent"
                 BorderThickness="0 0 0 2" BorderBrush="Black" MaxLength="20" Margin="64,90,63,330" Grid.ColumnSpan="2" PreviewTextInput="txtFIO_PreviewTextInput"/>

            <TextBlock x:Name="txtfirstreg" Text="Имя" FontSize="18" FontFamily="Century Gothic" Foreground="Gray" Margin="64,134,63,286" Grid.ColumnSpan="2" />
            <TextBox TextChanged="txtchangedLogin" x:Name="vvod_FNAME" FontSize="18" FontFamily="Century Gothic" Background="Transparent"
                 BorderThickness="0 0 0 2" BorderBrush="Black" MaxLength="20" Margin="64,134,63,286" Grid.ColumnSpan="2" PreviewTextInput="txtFIO_PreviewTextInput"/>

            <TextBlock x:Name="txtmiddlereg" Text="Отчество" FontSize="18" FontFamily="Century Gothic" Foreground="Gray" Margin="64,178,63,242" Grid.ColumnSpan="2" />
            <TextBox TextChanged="txtchangedLogin" x:Name="vvod_MNAME" FontFamily="Century Gothic" FontSize="18" Background="Transparent"
                 BorderThickness="0 0 0 2" BorderBrush="Black" MaxLength="20" Margin="64,178,63,242" Grid.ColumnSpan="2" PreviewTextInput="txtFIO_PreviewTextInput"/>

            <TextBlock x:Name="txtloginreg" Text="Логин" FontSize="18" FontFamily="Century Gothic" Foreground="Gray" Margin="64,222,63,198" Grid.ColumnSpan="2" />
            <TextBox TextChanged="txtchangedLogin" x:Name="vvod_login_reg" FontFamily="Century Gothic" Background="Transparent" FontSize="18"
                 BorderThickness="0 0 0 2" BorderBrush="Black" MaxLength="20" Margin="64,222,63,198" Grid.ColumnSpan="2" PreviewTextInput="txtPasswordLogin_PreviewTextInput"/>

            <TextBlock x:Name="txtpassreg" Text="Пароль" FontSize="18" FontFamily="Century Gothic" Foreground="Gray" Margin="64,266,63,154" Grid.ColumnSpan="2" />
            <PasswordBox PasswordChanged="passchangedPass" x:Name="vvod_pass_reg" Background="Transparent" FontSize="18"
                     BorderThickness="0 0 0 2" BorderBrush="Black" MaxLength="20" Margin="64,266,63,154" Grid.ColumnSpan="2" PreviewTextInput="txtPasswordLogin_PreviewTextInput"/>

            <Button x:Name="registr2" Content="Зарегистрироваться" FontFamily="Century Gothic" Background="Black" Foreground="White" FontSize="18" Click="btn_regist2" Margin="101,333,102,64" Grid.ColumnSpan="2"/>
        </Grid>
    </Grid>
</Window>