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| Title | Parse user-entered values in Visual Basic .NET |
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| Description | This example shows how to parse user-entered values in Visual Basic .NET. |
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| Keywords | parse, parse values, entered text, user-entered text, Visual Basic .NET, VB.NET |
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| Categories | Strings |
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You can use a data type's Parse method to convert text entered by the user into a value with the data type. For example, the following code converts the text in the txtInt textbox into an Integer.
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Private Sub txtInt_TextChanged(ByVal sender As _
System.Object, ByVal e As System.EventArgs) Handles _
txtInt.TextChanged
Try
Dim value As Integer = Integer.Parse(txtInt.Text)
lblInt.Text = value.ToString()
Catch
lblInt.Text = "Error"
End Try
End Sub
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Note that the code uses a "try catch" block to protect itself from user errors. You should always use error handling when parsing user-entered values.
This technique works reasonably well for most data types but there is one catch for currency values. Normally programs store currency values in the Decimal data type because it has the right amount of precision. However, Decimal.Parse does not automatically recognize currency formats. For example, it gets confused if the user enters $12.34. That sometimes makes programs look odd because they can easily display currency values but cannot read them.
The solution is to pass a second parameter to Decimal.Parse that tells it to allow any recognizable numeric format.
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Private Sub txtDecimal2_TextChanged(ByVal sender As _
System.Object, ByVal e As System.EventArgs) Handles _
txtDecimal2.TextChanged
Try
Dim value As Decimal = Decimal.Parse( _
txtDecimal2.Text, _
System.Globalization.NumberStyles.Any)
lblDecimal2.Text = value.ToString()
Catch
lblDecimal2.Text = "Error"
End Try
End Sub
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