What does this code do explanation? VB.NET - vb.net

Question

If Not (Char.IsDigit(e.KeyChar) Or Char.IsControl(e.KeyChar) Or (e.KeyChar = "." And Not point) Or (e.KeyChar = ",") Or (e.KeyChar = "-" And TQ.SelectionStart = 0))
VB.NET

Answer 1

Part 1
Char.IsDigit(e.KeyChar)
This checks if the current key character is a digit. Documentation on Char.IsDigit: https://learn.microsoft.com/en-us/dotnet/api/system.char.isdigit
Part 2
Char.IsControl(e.KeyChar)
This checks if the current key character is a formatting or other non-printing characters. Documentation on Char.IsControl: https://learn.microsoft.com/en-us/dotnet/api/system.char.iscontrol
Part 3
(e.KeyChar = "." And Not point)
This checks if the current key character is a period, though there is some implicit conversion going on here because KeyChar is a Char type and "." is defined as a String. I'm not sure what point is because you didn't include that definition, but it is most likely a Boolean variable.
Part 4
e.KeyChar = ","
This checks if the current key character is a comma, but again it is implicitly converting the KeyChar to a String.
Part 5
e.KeyChar = "-" And TQ.SelectionStart = 0
This checks if the current key character is a dash, using the implicit conversion. I'm not sure what TQ is because you didn't include that definition, but it is most likely inherited from TextBoxBase since SelectionStart (documentation) is a commonly used property.
Part 6
... Or ... Or ...
These are Or logical operators, it returns the entire grouping of conditions as true if any one of the conditions are true. I would actually suggest using the short-circuit operator OrElse instead. The reason for this is that Or will continue to evaluate the other conditions even if one of the earlier conditions are True when there is no need whereas OrElse will not bother to evaluate the other conditions. For example:
Dim value = 1
If (value = 1 Or value = 2 Or value = 3 Or value = 4) Then
' this does 4 checks because it is using Or, even though the first check was true
End If
If (value = 1 OrElse value = 2 Orelse value = 3 OrElse value = 4) Then
' this does 1 check because it is using OrElse and the first check was true
End If