Question

I’m trying to add custom properties to a workbook I have created programmatically. I have a method in place for getting and setting properties, but the problem is the workbook is returning null for the CustomDocumentProperties property. I cannot figure out how to initialize this property so that I can add and retrieve properties from the workbook. Microsoft.Office.Core.DocumentProperties is an interface, so I cant go and do the following

if(workbook.CustomDocumentProperties == null)
    workbook.CustomDocumentProperties = new DocumentProperties;

Here is the code I have to get and set the properties:

     private object GetDocumentProperty(string propertyName, MsoDocProperties type)
    {
        object returnVal = null;

        Microsoft.Office.Core.DocumentProperties properties;
        properties = (Microsoft.Office.Core.DocumentProperties)workBk.CustomDocumentProperties;

        foreach (Microsoft.Office.Core.DocumentProperty property in properties)
        {
            if (property.Name == propertyName && property.Type == type)
            {
                returnVal = property.Value;
            }
            DisposeComObject(property);
        }

        DisposeComObject(properties);

        return returnVal;
    }

    protected void SetDocumentProperty(string propertyName, string propertyValue)
    {
        DocumentProperties properties;
        properties = workBk.CustomDocumentProperties as DocumentProperties;

        bool propertyExists = false;
        foreach (DocumentProperty prop in properties)
        {
            if (prop.Name == propertyName)
            {
                prop.Value = propertyValue;
                propertyExists = true;
            }
            DisposeComObject(prop);

            if(propertyExists) break;
        }

        if (!propertyExists)
        {
            properties.Add(propertyName, false, MsoDocProperties.msoPropertyTypeString, propertyValue, Type.Missing);
        }

        DisposeComObject(propertyExists);

    }

The line
properties = workBk.CustomDocumentProperties as DocumentProperties;
always set properties to null.

This is using Microsoft.Office.Core v12.0.0.0 and Microsoft.Office.Interop.Excell v12.0.0.0 (Office 2007)

Answer 1

I looked at my own code and can see that I access the properties using late binding. I can’t remember why, but I’ll post some code in case it helps.

object properties = workBk.GetType().InvokeMember("CustomDocumentProperties", BindingFlags.Default | BindingFlags.GetProperty, null, workBk, null);

object property = properties.GetType().InvokeMember("Item", BindingFlags.Default | BindingFlags.GetProperty, null, properties, new object[] { propertyIndex });

object propertyValue = property.GetType().InvokeMember("Value", BindingFlags.Default | BindingFlags.GetProperty, null, propertyWrapper.Object, null);

EDIT: ah, now I remember why. 🙂

EDIT 2: Jimbojones’ answer – to use the dynamic keyword – is a better solution (if you value ease-of-use over the performance overhead of using dynamic).