自定义Converter

一般转换器

xmlns:cvt="clr-namespace:Project1.Common.Converter"

<UserControl.Resources>
   <BooleanToVisibilityConverter x:Key="boolToVisibilityConverter"/>
   <cvt:IsNullOrEmptyConverter  x:Key="isNullOrEmptyConverter " />
</UserControl.Resources>

Half

IsNullOrEmpty

using System;
using System.Globalization;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Media;
internal class IsNullOrEmptyConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return string.IsNullOrEmpty((string)value);
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return DependencyProperty.UnsetValue;
    }
}

Number2PercentageConverter

public class Number2PercentageConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        if (values == null || values.Length != 2) return .0;

        var obj1 = values[0];
        var obj2 = values[1];

        if (obj1 == null || obj2 == null) return .0;

        var str1 = values[0].ToString();
        var str2 = values[1].ToString();

        var v1 = str1.Value<double>();
        var v2 = str2.Value<double>();

        if (MathHelper.IsVerySmall(v2)) return 100.0;

        return v1 / v2 * 100;
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

String2VisibilityConverter

public class String2VisibilityConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return string.IsNullOrEmpty((string)value) ? Visibility.Collapsed : Visibility.Visible;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value != null && (Visibility)value == Visibility.Collapsed;
    }
}

ImagePathConverter

public class ImagePathConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        string path = (string)value;
        if (!string.IsNullOrEmpty(path))
        {
            return new System.Windows.Media.Imaging.BitmapImage(new Uri(path, UriKind.RelativeOrAbsolute));
        }
        else
        {
            return null;
        }

    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return null;
    }
}

IndentConverter

public class IndentConverter : IValueConverter
{

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        double colunwidth = 10;
        double left = 0.0;


        UIElement element = value as TreeViewItem;
        while (element.GetType() != typeof(TreeView))
        {
            element = (UIElement)VisualTreeHelper.GetParent(element);
            if (element.GetType() == typeof(TreeViewItem))
                left += colunwidth;
        }
        return new Thickness(left, 0, 0, 0);
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }

}

TransparentColorConverter

Color="{Binding SolidColorBrushKey1, Converter={StaticResource transparentColorConverter}, ConverterParameter=0.12}"

/// <summary>
/// 设置颜色透明度
/// </summary>
public class TransparentColorConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value is SolidColorBrush brush && parameter is string txt)
        {
            var alpha = txt.Value<double>();
            var a = alpha * 255;
            return Color.FromArgb((byte)a, brush.Color.R, brush.Color.G, brush.Color.B);
        }
        return DependencyProperty.UnsetValue;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}