When you publish a Infopath Form to a sharepoint list, the Infopath form contains some fields (text and date(time) data types). These fields are copied to a sharepoint list when you publish the form to it.
You should think sharepoint keeps the data types like in the infopath form, but this isn't, I noticed that the date(time) data type is just a string/text field in the sharepoint list!
The strange thing is that when you add a column in the published list manualy (for example a datetime field), it will keep the data type and not change it to a string.
I noticed it when a wanted to perform an update an a field called ApprovalDate (Date Datatype) in a Web Part:
SPSite site = new SPSite("http://......");
SPListItemCollection results = site.Lists["InfopathPublishedList"].Items;
foreach (SPListItem item in results)
item.Properties["ApprovalDate"] = DateTime.Today;//DateTime.Today.ToString();
This code failed when I did this on the datetime field published by infopath:
Error:Specified data type does not match the current data type of the property. at Microsoft.SharePoint.Utilities.SPUtility.UpdateArrayFromHashtable(Object& o, Hashtable ht) at Microsoft.SharePoint.SPListItem.PrepareItemForUpdate(Guid newGuidOnAdd, Boolean bMigration, Boolean& bAdd, Boolean& bPublish, Object&
objAttachmentNames, Object& objAttachmentContents, Int32& parentFolderId) at Microsoft.SharePoint.SPListItem.UpdateInternal(Boolean bSystem, Boolean bPreserveItemVersion, Guid newGuidOnAdd, Boolean bMigration,
Boolean bPublish, Boolean bNoVersion, Boolean bCheckOut, Boolean bCheckin, Boolean suppressAfterEvents) at Microsoft.SharePoint.SPListItem.Update()
This doesn't happen if the ApprovalDate is added by create column in the list.
So watch out, and as you notice in the picture below: It ain't what it look like........