Convertir cadena a doble - VB

Question

¿Hay un método eficiente en VB para comprobar si una cadena se puede convertir a una doble?

Actualmente estoy haciendo esto al tratar de convertir la cadena a un doble y luego ver si arroja una excepción. Pero esto parece estar ralentizando mi aplicación.

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 

Answer 1

Trate de mirar Double.TryParse() si está utilizando .NET 1,1/2,0/3,0/3,5/4,0/4,5

Answer 2

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 

Answer 3

VB.NET código de ejemplo

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 

Answer 4

Las versiones internacionales:

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 

Resultados:

 ' 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