How can you ever update a value in CustomProperties collection in Excel VSTO?

I'm working on an Excel Addon using VSTO. I've just run into a weird problem, if I try get a value from the CustomProperties it throws a COM exception and I have no idea why. Has anyone run into this? Here's the code I'm trying to use:

CustomProperties properties = worksheet.CustomProperties;
properties.Add("name", "value");
Console.Write(properties["name"]); //this crashes COMException. Type mismatch. (Exception from HRESULT: 0x80020005 (DISP_E_TYPEMISMATCH))
Console.Write(properties[0]); //and this crashes COMException.Exception from HRESULT: 0x800A03EC
Console.Write(properties.Item[0]); //and this also crashes Exception from HRESULT: 0x800A03EC
Console.Write(properties.Item["name"]); //and this crashes as well Type mismatch.
Console.Write(properties.get_Item(0)); //this crashes again HRESULT: 0x800A03EC
Console.Write(properties.get_Item("name"); //and this still crashes Type mismatch.

I have no idea how to work with this collection. I found a workaround to read the properties:

Dictionary<string, string> workingProperties = new Dictionary<string, string>();
foreach (dynamic custProp in properties)
   workingProperties.Add(custProp.Name, custProp.Value);
string value = workingProperties["name"];// this works

However, when it comes to updating an existing property - I'm stuck, I need a way to address an item in that collection, and there's no Remove or Delete function to first remove it and then add a new one with the same name.

Ok, was writing this post and realized a workaround:

        string GetProperty(Worksheet ws, string name)
        {            
            foreach (CustomProperty cp in ws.CustomProperties)
                if (cp.Name == name)
                    return cp.Value;
            return null;
        }
        void SetProperty(Worksheet ws, string name, string value)
        {            
            bool found = false;
            CustomProperties cps = ws.CustomProperties;
            foreach (CustomProperty cp in cps)
            {
                if (cp.Name == name)
                {
                    found = true;
                    cp.Value = value;
                }
            }
            if (!found)
                cps.Add(name, value);       
        }

Still, very weird that there's no way to access the collection in a normal way.