Database data type float to C # type decimal, float data type conversion is invalid

An error occurred while running the system today. The data type conversion is invalid. data. sqlclient. in the get_decimal () method, an error occurs when the Float Type of the database is converted to the decimal type of C #. The entity class uses decimal? Type, even if the value in the database is null, the conversion error cannot occur.

There are a variety of searches on the Internet. Many people encounter similar situations, most of which are errors when they directly go to the float type, such as (float) Dr [0]. Later I saw that it should be converted to double first, then you can convert it to float.

I tried decimal of the object class? Type field to double? Type, OK.