Writing tag values to a file

[hans gerritsen]

The panel application is being used in several plants. Each plant has it's own settings. I want to make a backup/restore script for all actual settings which are being saved to harddisk or usb of the T21C-panel. (Recipes are unfortunately limited to 256 variable and I need a lot more.)
With the following script I can save settings to a file:

public void SaveSettings(string path)
{
try {
using (StreamWriter Saving = new StreamWriter(path))
{
Saving.WriteLine(Globals.Tags.<tagname>.FullName.ToString()); Saving.WriteLine(Globals.Tags.<tagname>.Value.ToString());
}
}
catch{
MessageBox.Show("Error while saving");
}
}
The problem is that I have to write one scriptline for each tag
Is there a possibility to make a loop which uses an tag[index] to write this info to a file? f.eks. "for (int i=0; i < ....Tags.Count....;i++)"

Or are there easier ways to make a .csv fil with all tagnames with values which can be read into the panel again?

[mark.monroe]

Check out this forum post on how to dynamically reference tags using C#.

[hans gerritsen]

Thanks for the links with several solutions.
As I understand the Globals.Tags object isn't a 'list' so it is not possible to loop through them. The other solutions given are based on a tag names which must have a kind of sequence in their names. Unfortunately this is not the case in my situation.

I think I have to create a kind manual taglist myself.
If I write the values of the tags to a file I have to be sure they contain the actual values in the plc. What can I do to make sure the values have been read from the plc before I write them to a file?

[mark.monroe]

You can call this function, which will force a tag read.

Code: Select all

Globals.Tags.MyTag.Read();

[hans gerritsen]

Thanks!
Another question:
I can use the script for "converting a string to a tag" (see below) to read a list of tag names from a file and write their actual values to a settings file.

public GlobalDataItem StringToTag(string tagName)
{
string typeName = (new GlobalDataItem()).GetType().Name;
PropertyInfo[] props = Globals.Tags.GetType().GetProperties();
foreach (PropertyInfo prop in props) {
if (prop.PropertyType.Name.Equals(typeName)) {
if (prop.Name.Equals(tagName, StringComparison.CurrentCultureIgnoreCase)) {
return (GlobalDataItem)prop.GetValue(Globals.Tags, null);
}
}
}
return null;
}

I want to be able to read such a settings file back into the panel.
How can I assign a value to a tag via the same method? So instead of using GetValue, can I use SetValue?.

[hans gerritsen]

" Globals.Tags.MyTag.Read(); "
Is it possible to use a script with a tag-string here instead of the specific tag name? Something like the script "String to Tag". Else I still have to write a scriptline for every tag name.

[mark.monroe]

Yes, it is possible to use a viable as a tag name and then call the Read() function. You need to look at the other forum post I mentioned above and read up on C# reflection. The SetValue is a C# function that is used to set the value of an an object.

[hans gerritsen]

Thanks Mark,
I found out how to do it!

[Patrick Hall]

If you are still interested in iterating or generating a list from the Globals.Tags class at runtime. Here is a Generic method I wrote for a recent project that uses Reflection to generate an IEnumerable<T> that can be used with foreach directly. You can convert it to a list if you like.

You can place the additional usings and paste the member function into the Tags Script window so that GetTags<T>() is a member of the Globals.Tags class.

Code: Select all

	// Additional Usings
	using System.Collections.Generic;
	using System.Reflection;
	using Neo.ApplicationFramework.Tools.OpcClient;

GetTags Method...

Code: Select all

		/// <summary>
		/// Gets an IEnumerable{T} collection of defined tags.
		/// </summary>
		/// <example>
		/// // An iterable collection of GlobalDataItem Tags.
		/// IEnumerable{GlobalDataItem} gTags = Globals.Tags.GetTags{GlobalDataItem}();
		/// 
		/// // An iterable collection of SystemDataItem Tags.
		/// IEnumerable{SystemDataItem} sTags = Globals.Tags.GetTags{SystemDataItem}();
		/// </example>		
		/// <returns>IEnumerable{T}</returns>
		public IEnumerable<T> GetTags<T>() where T:GlobalDataItem {
			// Gets PropertyInfo array using reflection
			PropertyInfo[] props = this.GetType().GetProperties();
			// Process all PropertyInfo objects found
			foreach (PropertyInfo prop in props) {				
				if (prop.PropertyType == typeof(T)) {
					yield return (T)prop.GetValue(this, null);					    
				}				
			}			
		}

Code docs show examples of how to get either User created tags, or System Specific Tags (if you actually added any).

If you had a ListBox added to a screen (named ListBox1) you could use the following code to populate the ListBox with the names of all tags found.

Code: Select all

			ListBox1.Items.Clear();			
			
			foreach(GlobalDataItem gdi in Globals.Tags.GetTags<GlobalDataItem>()){
				ListBox1.Items.Add(string.Format("{0}={1}",gdi.Name, gdi.Value));
			}

Obtaining the Value of each tag in the sequence can be done by using gdi.Value (keep in mind it is of type VariantValue)

DynamicTagList.png (20.67 KiB) Viewed 36653 times

[hans gerritsen]

Hi Patrick,

I have already a working version but your solution would much much better!!
But I only need those tags which are ReadWrite or Write and I have to know what kind of type it is (Bool, INT16, etc). I can't find how to do that.

Thanks in advance.