How to declare a fixed-length string in VB.NET?

Question

How do i Declare a string like this:

Dim strBuff As String * 256

in VB.NET?

Answer 1

You can use Microsoft.VisualBasic.Compatibility:

Imports Microsoft.VisualBasic.Compatibility

Dim strBuff As New VB6.FixedLengthString(256)

But it's marked as obsolete and specifically not supported for 64-bit processes, so write your own that replicates the functionality, which is to truncate on setting long values and padding right with spaces for short values. It also sets an "uninitialised" value, like above, to nulls.

Sample code from LinqPad (which I can't get to allow Imports Microsoft.VisualBasic.Compatibility I think because it is marked obsolete, but I have no proof of that):

Imports Microsoft.VisualBasic.Compatibility

Dim U As New VB6.FixedLengthString(5)
Dim S As New VB6.FixedLengthString(5, "Test")
Dim L As New VB6.FixedLengthString(5, "Testing")
Dim p0 As Func(Of String, String) = Function(st) """" & st.Replace(ChrW(0), "\0") & """"
p0(U.Value).Dump()
p0(S.Value).Dump()
p0(L.Value).Dump()
U.Value = "Test"
p0(U.Value).Dump()
U.Value = "Testing"
p0(U.Value).Dump()

which has this output:

"\0\0\0\0\0"
"Test "
"Testi"
"Test "
"Testi"