Xaml StringFormat and static strings

Question

I want to see if theres a way to combine datetime string format and static strings.

So currently I can format my date and prefix with text like this:

<TextBlock Text="{Binding MyDate StringFormat=Started {0:dd-MMM-yyyy HH:mm}}"

Results in this:

Started 01-Jan-2011 12:00

In the past I've been able to use a static string to keep a common format for my dates; like this (Note no prefixed text):

<TextBlock Text="{Binding MyDate, StringFormat={x:Static i:Format.DateTime}}" />

Where i:Format is a static class with a static property DateTime that returns the string "dd-MMM-yyyy HH:mm"

So what I'm asking; is there a way to combine these methods so that I can prefix my date and use the common static string formatter?

Josh G · Accepted Answer · 2011-04-08 12:04:25Z

2

You could use something like this in place of the Binding:

public class DateTimeFormattedBinding : Binding {
    private string customStringFormat = "%date%";

    public DateTimeFormattedBinding () {
        this.StringFormat = Format.DateTime;
    }

    public DateTimeFormattedBinding (string path)
        : base(path) {
        this.StringFormat = Format.DateTime;
    }

    public string CustomStringFormat {
        get {
            return this.customStringFormat;
        }
        set {
            if (this.customStringFormat != value) {
                this.customStringFormat = value;
                if (!string.IsNullOrEmpty(this.customStringFormat)) {
                    this.StringFormat = this.customStringFormat.Replace("%date%", Format.DateTime);
                }
                else {
                    this.StringFormat = string.Empty;
                }
            }
        }
    }
}

Then use it like {local:DateTimeFormattedBinding MyDate, CustomStringFormat=Started %date%}

You could probably make the replacement generic also, and set it via a different property (or properties).

edited Apr 8, 2011 at 12:04

Josh G

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answered Apr 8, 2011 at 11:31

CodeNaked

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1 Comment

Josh G Over a year ago

I think this is the only alternative if you want to fill both the value and the format of the value. I tried string.Format("Started {0:{1}}", DateTime.Now, "dd-MMM-yyyy HH:mm") and got an exception.

jrivam · Accepted Answer · 2014-07-15 06:10:47Z

you could use a converter like this:

<TextBlock>
    <TextBlock.Text>
                <MultiBinding Converter="{StaticResource StringFormatConcatenator}">
                        <Binding Source="Started {0}"/>
                        <Binding Source="{x:Static i:Format.DateTime}"/>                                        
                        <Binding Path="MyDate"/>
                </MultiBinding>
    </TextBlock.Text>
</TextBlock>

public class StringFormatConcatenator : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        string format = values[0].ToString();
        for (int i = 0; i < (values.Length - 1) / 2; i++)
            format = format.Replace("{" + i.ToString() + "}", "{" + i.ToString() + ":" + values[(i * 2) + 1].ToString() + "}");

        return string.Format(format, values.Skip(1).Select((s, i) => new { j = i + 1, s }).Where(t => t.j % 2 == 0).Select(t => t.s).ToArray());
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
    {
        return new string[] { };
    }
}

You can add as many variables to format as needed in pair of (format, value)

Where:

Binding 0: the complete format without specific variable format ({0:dd-MMM-yyyy HH:mm} replaced by {0})

Binding odd (1,3,5...): variable specific format ("dd-MMM-yyyy HH:mm")

Binding even (2,4,6...): variable value (MyDate)

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