tasks/daily_planner/MainWindow.xaml

<Window x:Class="daily_planner.MainWindow"
        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:daily_planner"
        mc:Ignorable="d"
        Title="Ежедневник" Height="500" Width="650" MinHeight="500" MinWidth="650">
    <Grid >
        

        <Grid.RowDefinitions>
            <RowDefinition Height="5*"/>
            <RowDefinition/>
            <RowDefinition/>
        </Grid.RowDefinitions>

        <DataGrid x:Name="tasksGrid" Grid.Row="0" AutoGenerateColumns="False" Margin="25, 0"
                  SelectionChanged="tasksGrid_SelectionChanged" FontFamily="Montserrat Medium">
            <DataGrid.Columns>
                <DataGridTextColumn Header="Задача" Binding="{Binding Task}" Width="*" IsReadOnly="True" 
                                    FontFamily="Montserrat Light"/>
                <DataGridTextColumn Header="Дедлайн" Binding="{Binding Deadline}" Width="*" IsReadOnly="True" 
                                    FontFamily="Montserrat Light"/>
                <DataGridCheckBoxColumn Header="Выполнение" Width="Auto"/>
            </DataGrid.Columns>
        </DataGrid>

        <Grid Grid.Row="1">
            <Grid.ColumnDefinitions>
                <ColumnDefinition/>
                <ColumnDefinition/>
                <ColumnDefinition/>
            </Grid.ColumnDefinitions>

            <Button Grid.Column="0" Content="Добавить" Background="#ebebeb" Margin="25, 15" Click="Insert_Click" 
                    FontFamily="Montserrat Medium" FontSize="14"/>
            <Button Grid.Column="1" Content="Изменить" Background="#ebebeb" Margin="25, 15" Click="Update_Click" 
                    FontFamily="Montserrat Medium" FontSize="14"/>
            <Button Grid.Column="2" Content="Удалить" Background="#ebebeb" Margin="25, 15" Click="Delete_Click" 
                    FontFamily="Montserrat Medium" FontSize="14"/>

        </Grid>

        <Grid Grid.Row="2" Background="White">
            <Grid.ColumnDefinitions>
                <ColumnDefinition/>
                <ColumnDefinition/>
            </Grid.ColumnDefinitions>

            <Label Grid.Column="0" Content="Задача" FontFamily="Montserrat Medium" Margin="25, 0"/>
            <TextBox x:Name="TbTask" Grid.Column="0" Margin="25, 30, 25, 10" 
                     VerticalContentAlignment="Center" FontFamily="Montserrat Light" />
            <Label Grid.Column="1" Content="Дедлайн" FontFamily="Montserrat Medium" Margin="25, 0"/>
            <DatePicker Name="DpDeadline" Grid.Column="1" Margin="25, 30, 25, 10"/>

        </Grid>

    </Grid>
</Window>