R – Problem setting property value on Custom Control Template Part

silverlight-3.0

I have a custom control template that contains a Slider control.
I name that as a part in the class that implements the custom control:

[TemplatePart(Name = MapZoomSliderName, Type = typeof(Slider))]

In the OnApplyTemplate() override, I get the Slider:

        MapZoomSlider = (Slider) GetTemplateChild("MapZoomSlider");
        if (null != MapZoomSlider)
        {

            MapZoomSlider.ValueChanged +=new RoutedPropertyChangedEventHandler<double>(MapZoomSlider_ValueChanged);
            MapZoomSlider.Value = InitSliderValue;  // crash
            _lastSliderValue = MapZoomSlider.Value;
        }

When I try to set the Slider's Value property, the app crashes with "Object reference not set to an instance of an object."
Getting the slider's value works as expected.
What do I need to do to set the Slider's value at run time?
Thanks for any tips…

Best Answer

What is "InitSliderValue"? Maybe its the wrong value type? (Must be a double) Also, zero or negative may not be a valid value.

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R – Automatically creating child objects during Silverlight DataBinding

There is no automatic way. You could consider using a pattern like M-V-VM and handling this logic in the ViewModel. You might also possibly get creative with an IValueConverter so that your binding can run custom code when the value is set. But WPF / Silverlight binding will not automatically do this work for you.

Python – Sending mail from Python using SMTP

The script I use is quite similar; I post it here as an example of how to use the email.* modules to generate MIME messages; so this script can be easily modified to attach pictures, etc.

I rely on my ISP to add the date time header.

My ISP requires me to use a secure smtp connection to send mail, I rely on the smtplib module (downloadable at http://www1.cs.columbia.edu/~db2501/ssmtplib.py)

As in your script, the username and password, (given dummy values below), used to authenticate on the SMTP server, are in plain text in the source. This is a security weakness; but the best alternative depends on how careful you need (want?) to be about protecting these.

=======================================

#! /usr/local/bin/python


SMTPserver = 'smtp.att.yahoo.com'
sender =     'me@my_email_domain.net'
destination = ['recipient@her_email_domain.com']

USERNAME = "USER_NAME_FOR_INTERNET_SERVICE_PROVIDER"
PASSWORD = "PASSWORD_INTERNET_SERVICE_PROVIDER"

# typical values for text_subtype are plain, html, xml
text_subtype = 'plain'


content="""\
Test message
"""

subject="Sent from Python"

import sys
import os
import re

from smtplib import SMTP_SSL as SMTP       # this invokes the secure SMTP protocol (port 465, uses SSL)
# from smtplib import SMTP                  # use this for standard SMTP protocol   (port 25, no encryption)

# old version
# from email.MIMEText import MIMEText
from email.mime.text import MIMEText

try:
    msg = MIMEText(content, text_subtype)
    msg['Subject']=       subject
    msg['From']   = sender # some SMTP servers will do this automatically, not all

    conn = SMTP(SMTPserver)
    conn.set_debuglevel(False)
    conn.login(USERNAME, PASSWORD)
    try:
        conn.sendmail(sender, destination, msg.as_string())
    finally:
        conn.quit()

except:
    sys.exit( "mail failed; %s" % "CUSTOM_ERROR" ) # give an error message

Best Answer

Related Solutions

R – Automatically creating child objects during Silverlight DataBinding

Python – Sending mail from Python using SMTP

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