VBには、文字列をdoubleに変換できるかどうかを確認するための効率的な方法がありますか?
現在、文字列をdoubleに変換して、例外がスローされるかどうかを確認することでこれを行っています。しかし、これは私のアプリケーションを遅くしているようです。
Try
' if number then format it.
current = CDbl(x)
current = Math.Round(current, d)
Return current
Catch ex As System.InvalidCastException
' item is not a number, do not format... leave as a string
Return x
End Try
.NET 1.1/2.0/3.0/3.5/4.0/4.5を使用している場合は、Double.TryParse()を見てみてください
VB.NETサンプルコード
Dim A as String = "5.3"
Dim B as Double
B = CDbl(Val(A)) '// Val do hard work
'// Get output
MsgBox (B) '// Output is 5,3 Without Val result is 53.0
Dim text As String = "123.45"
Dim value As Double
If Double.TryParse(text, value) Then
' text is convertible to Double, and value contains the Double value now
Else
' Cannot convert text to Double
End If
国際版:
Public Shared Function GetDouble(ByVal doublestring As String) As Double
Dim retval As Double
Dim sep As String = CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator
Double.TryParse(Replace(Replace(doublestring, ".", sep), ",", sep), retval)
Return retval
End Function
' NULLABLE VERSION:
Public Shared Function GetDoubleNullable(ByVal doublestring As String) As Double?
Dim retval As Double
Dim sep As String = CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator
If Double.TryParse(Replace(Replace(doublestring, ".", sep), ",", sep), retval) Then
Return retval
Else
Return Nothing
End If
End Function
結果:
' HUNGARIAN REGIONAL SETTINGS (NumberDecimalSeparator: ,)
' Clean Double.TryParse
' -------------------------------------------------
Double.TryParse("1.12", d1) ' Type: DOUBLE Value: d1 = 0.0
Double.TryParse("1,12", d2) ' Type: DOUBLE Value: d2 = 1.12
Double.TryParse("abcd", d3) ' Type: DOUBLE Value: d3 = 0.0
' GetDouble() method
' -------------------------------------------------
d1 = GetDouble("1.12") ' Type: DOUBLE Value: d1 = 1.12
d2 = GetDouble("1,12") ' Type: DOUBLE Value: d2 = 1.12
d3 = GetDouble("abcd") ' Type: DOUBLE Value: d3 = 0.0
' Nullable version - GetDoubleNullable() method
' -------------------------------------------------
d1n = GetDoubleNullable("1.12") ' Type: DOUBLE? Value: d1n = 1.12
d2n = GetDoubleNullable("1,12") ' Type: DOUBLE? Value: d2n = 1.12
d3n = GetDoubleNullable("abcd") ' Type: DOUBLE? Value: d3n = Nothing
私はEval(string)
を単純に使用し、Doubleと評価しました。