instead of your

if (propType.IsGenericType &&
propType.GetGenericTypeDefinition() == typeof(Nullable<>))
{
propType = Nullable.GetUnderlyingType(propType);
}

you could also do

column.DataType = Nullable.GetUnderlyingType(PropertyType) ?? PropertyType;

depending on your knowledge about the ?? operator and your preferences it could improve the readability