Question

我喜欢用不同的公式填充数据库。

当我在数据库中有一个"(2+4)*5"之类的公式时，得到的结果40：

update DB.dbo.INFOGROUP SET formula = '(2+4)*5' where INFOGROUP = 'S42'

当我在数据库中有一个"(x+4)*5"之类的公式时，我得到的结果是20。即使将x的值设置为x，也会忽略10的值：

update DB.dbo.INFOGROUP SET formula = '(x+4)*5' where INFOGROUP = 'S42'

Private Sub BtnCalculate_Click(sender As Object, e As EventArgs) Handles BtnCalculate.Click
    Dim SC As New MSScriptControl.ScriptControl
    Dim x As Double = 10
    SQL.AddParam("@infogroup", "S42")
    SQL.ExecQuery($"SELECT formula FROM DB.dbo.INFOGROEP where infogroep=@infogroep")
    Dim Formula As String = <string_from_db>
    'SET LANGUAGE TO VBSCRIPT
    SC.Language = "VBSCRIPT"
    'ATTEMPT MATH
    Try
        Dim Result As Double = Convert.ToDouble(SC.Eval(Formula))
        'SHOW THAT IT WAS VALID
        MessageBox.Show("Math success, " & Formula & " equals " & Result.ToString)
    Catch ex As Exception
        'SHOW THAT IT WAS INVALID
        MessageBox.Show("Not a valid math formula for a double.")
    End Try
End Sub

这完全有可能吗？或者我需要第三方脚本吗？

顺便说一句：在Visual Foxpro中，有一个类似EVAL(db_string)的函数。

Answer 1

脚本引擎不了解方法中的变量。如果要评估包含变量的公式，则需要告诉它该变量具有什么值：

SC.Language = "VBSCRIPT"
sc.AddCode "Private Const x = 10"

Dim Result As Double = Convert.ToDouble(SC.Eval(Formula))

VB.NET使用变量评估字符串

1 个答案: