crm 4.0 - Set stringproperty to null/blank using the SDK service

HI,

I am using CRM 4.0 on premise version. I have one attribute of type string. I need to set its value blank/null using sdk service. I am using following code to set value in attribute of  string type. But it gives me error while calling service.Update method.

StringProperty strPrpstring =newStringProperty("new_test",string.Empty);

deUpdatedData.Properties["new_test"] = strPrpstring;

service.Update(deUpdatedData);