Incompatible data type

With PostgreSQL, when retrieving data into a DataWindow that uses stored procedure as its data source, an error occurred:

Select Error: The Decimal type is not compatible with the data type of the mapped property 'Unit_Weight' on model 'Dw_Mat_Items_Inquiry_List'.

Debugging technique:

Search for the model ”Dw_Mat_Items_Inquiry_List” in SnapDevelop and then “Unit_Weight” in the model .cs file. In the stored procedure of the DataWindow, the data type of Unit_Weight is NUMBER (12,3). According to the Data type mapping tables, the Number data type is mapped to decimal. Therefore, the data type of Unit_Weight shall be changed to decimal in the .cs file:

Public decimal? Unit_Weight { get; set; }