Cannot implicitly convert 'string' to 'System.TypeCode'

问题

Just wondering if anyone knows how to fix this error? I've also used TypeCode. but still no luck. Thanks

case typeof(Nullable<int>).ToString(): //<----- error is here
if ((!object.ReferenceEquals(value, DBNull.Value)))
{
    return value;
}
else
{
    return null;
}

This is the switch

    public static object HandleDBNull(object value, System.Type _type)
{
    switch (Type.GetTypeCode(_type))
    {

Thanks again for any help

回答1:

Ultimately, typeof(Nullable<int>) isn't a TypeCode, and the string representation of that isn't a TypeCode. There is no TypeCode that represents Nullable<int> specifically.

You can use Nullable.GetUnderlyingType(type) to check that something is Nullable<T> and get the T at the same time (it returns null if not), and you can use Type.GetTypeCode on the result of that, but: I suspect that in your case, using TypeCode at all may be an error, and simply checking the type itself (if (type == typeof(int?)) {...}) may be better.

回答2:

The type you use in the switch statement has to match the type in the case statements, where currently you're comparing a TypeCode to a string.

The TypeCode enumeration only contains values for the primitive types, and all others will be TypeCode.Object. So you can't get a specific TypeCode for the Nullable<int> type.

来源：https://stackoverflow.com/questions/44671596/cannot-implicitly-convert-string-to-system-typecode