Accessing folder properties are but different from SharePoint list item access. Following code demonstrates the basics.
Create SharePoint Folder with Properties
using (var clientContext = ypurMethodToGetSpContectt() )
{
var lst = clientContext.Web.Lists.GetByTitle("ListName");
var folder = lst.RootFolder.Folders.Add("FolderName");
folder.Properties["property1"] = "sample";
folder.Properties["property1"] = "sample";
folder.Update();
clientContext.ExecuteQuery();
}
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