VB.NET 用变量评估字符串

Question

我喜欢用不同的公式填充我的数据库。

当我在数据库中有一个像 "(2+4)*5" 这样的公式时，我得到的结果是 40:

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

当我在数据库中有一个像 "(x+4)*5" 这样的公式时，我得到了结果 20。即使我将 x 的值设置为 10:

，x 值也会被忽略

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

这是否可能，或者我需要第三方脚本吗？

顺便说一句：在 Visual Foxpro 中有一个像 EVAL(db_string).

这样的函数

Answer 1

脚本引擎不知道您的方法中的变量。如果要计算包含变量的公式，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 用变量评估字符串

VB.NET Evaluate a string with variables

vb.net

expression

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msscriptcontrol