我自己解决了 VB2005里有个算法 可以直接用
Dim x As SqlTypes.SqlDouble = Me.TextBox5.Text
Dim y As SqlTypes.SqlDouble = Me.TextBox8.Text
Dim returnValue As SqlTypes.SqlDouble
returnValue = SqlTypes.SqlDouble.Multiply(x, y)
Me.TextBox9.Text = returnValue
先引入命名空间Imports System.Data.SqlTypes.SqlDouble