動的コードの実行：String - >ランタイムコードVB.net

Question

実行時に文字列の中でいくつかのコードを実行しようとしています。 I.

Dim code As String = "IIf(1 = 2, True, False)" 

code文字列内でコードを実行するにはどうすればよいですか？

Answer 1

@ElektroStudiosが言ったように、これを行う適切な方法はCodeDom compilerを使用することですが、これはこれほど単純なものでは少し残忍です。

することはできソートのカンニング例えばのでDataColumn Expression

のパワーを活用：

Public Function EvaluateExpression(Of T, K)(input As T, formula As String) As K 
    'add a columns to hold the value 
    Dim colStatus As New DataColumn 
    With colStatus 
     .DataType = GetType(T) 
     .ColumnName = "Condition" 
    End With 

    'add a column to compute the expression 
    Dim colExp As New DataColumn 
    With colExp 
     .DataType = GetType(K) 
     .ColumnName = "Expression" 
     .Expression = formula 
    End With 

    'create a table and add the columns 
    Dim dt As New DataTable 
    With dt.Columns 
     .Add(colStatus) 
     .Add(colExp) 
    End With 

    'now add a row and set the condition to the value we have 
    Dim row As DataRow = dt.NewRow 
    row.SetField(Of T)("Condition", input) 
    dt.Rows.Add(row) 

    'now read back the computed value based on the expression being evaluated 
    Return row.Field(Of K)("Expression") 
End Function 

：あなたはこのような、より一般的な関数にこのすべてを包むことができ

Dim formula = "IIF(Condition = 'Yes', 'Go', 'Stop')" 
    Dim value As String = "Yes" 
    Dim result As String 

    'add a columns to hold the value 
    Dim colStatus As New DataColumn 
    With colStatus 
     .DataType = System.Type.GetType("System.String") 
     .ColumnName = "Condition" 
    End With 

    'add a column to compute the expression 
    Dim colExp As New DataColumn 
    With colExp 
     .DataType = System.Type.GetType("System.String") 
     .ColumnName = "Expression" 
     .Expression = formula 
    End With 

    'create a table and add the columns 
    Dim dt As New DataTable 
    With dt.Columns 
     .Add(colStatus) 
     .Add(colExp) 
    End With 

    'now add a row and set the condition to the value we have 
    Dim row As DataRow = dt.NewRow 
    row.SetField(Of String)("Condition", value) 
    dt.Rows.Add(row) 

    'now read back the computed value based on the expression being evaluated 
    result = row.Field(Of String)("Expression") 
    MessageBox.Show(result) 

それで、あなたは次のように呼び出すことができます：

Dim result = EvaluateExpression(Of Integer, Boolean)(1, "IIF(Condition = 1, True, False)")