Concatenating Strings (do not want to concatenate empty strings)

Question

I have 5 string variables, and i have a moment which I want to store (concatenate) them into one with ; separator. but some of them sometimes might be empty ( "" ) and i want to skip them. so far I have this code

  If ACL_PermissionFC.Length > 0 Then ACL_PermissionFC = ACL_PermissionFC.PadLeft(PaddingValue) & " [" & ACL_Type & "]" Else ACL_PermissionFC = ""

        If ACL_PermissionM.Length > 0 Then ACL_PermissionM = ACL_PermissionM.PadLeft(PaddingValue) & " [" & ACL_Type & "]" Else ACL_PermissionM = ""

        If ACL_PermissionRE.Length > 0 Then ACL_PermissionRE = ACL_PermissionRE.PadLeft(PaddingValue) & " [" & ACL_Type & "]" Else ACL_PermissionRE = ""

 If ACL_PermissionRE.Length > 0 Then ACL_PermissionRE = ACL_PermissionRE.PadLeft(PaddingValue) & " [" & ACL_Type & "]" Else ACL_PermissionRE = ""

        If ACL_PermissionLD.Length > 0 Then ACL_PermissionLD = ACL_PermissionLD.PadLeft(PaddingValue) & " [" & ACL_Type & "]" Else ACL_PermissionLD = ""

dim Permissions as String               
Permissions= ACL_PermissionFC & ";" & ACL_PermissionFC & ";" & ACL_PermissionRE & ";" & ACL_PermissionLD & ";" & ACL_PermissionR & ";" & ACL_PermissionW

And when there are empty strings i get this ;;Has Read & Execute security [Allow];Has List Folder Contents security [Allow];Has Read security

how can i make it when a string is empty not to concatenate it? ( i dont want double ; or tripple)

A class or List for 5 things so closely related would seem to be more appropriate than 5 independent vars (or Dictionary or even an array) — Ňɏssa Pøngjǣrdenlarp
– Ňɏssa Pøngjǣrdenlarp, Commented Mar 10, 2015 at 14:39

sloth · Accepted Answer · 2015-03-10 15:30:26Z

4

Use String.Join together with Where/Select and String.IsNullOrWhitespace:

Dim items = From item In {ACL_PermissionFC, ACL_PermissionM, ACL_PermissionRE, ACL_PermissionW, ACL_PermissionLD} 
            Where Not String.IsNullOrWhiteSpace(item)
            Select String.Format("{0}[{1}]", item.PadLeft(PaddingValue), ACL_Type)

Dim Permissions = String.Join(";", items)

edited Mar 10, 2015 at 15:30

answered Mar 10, 2015 at 14:40

sloth

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Tim Schmelter Over a year ago

Although the one-liner works i prefer a more readable version ;)

Daren Beattie · Accepted Answer · 2015-03-10 14:46:45Z

1

Edit: It looks like sloth isn't living up to his namesake. He posted pretty much the same answer while I was still checking syntax.

You can use Linq to eliminate the empty strings, and String.Join() to concatenate them:

Dim Permissions As String = String.Join(";", { ACL_PermissionFC, ACL_PermissionM, ACL_PermissionRE, ACL_PermissionLD, ACL_PermissionW }.Where(Function(acl) Not String.IsNullOrWhiteSpace(acl)).ToArray())

Caveat: My Visual Studio is freaking out again, so I haven't tested the above for accuracy.

answered Mar 10, 2015 at 14:46

Daren Beattie

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Tim Schmelter Over a year ago

You are too late. Also, ToArray is redundant if you use at least NET 4.

Michael Mahony · Accepted Answer · 2015-03-10 14:58:22Z

How about trimming the string first?

If ACL_PermissionFC.Trim() <> "" Then ACL_PermissionFC = ACL_PermissionFC.PadLeft(PaddingValue) & " [" & ACL_Type & "]" Else ACL_PermissionFC = ""

        If ACL_PermissionM.Trim() <> "" Then ACL_PermissionM = ACL_PermissionM.PadLeft(PaddingValue) & " [" & ACL_Type & "]" Else ACL_PermissionM = ""

        If ACL_PermissionRE.Trim() <> "" Then ACL_PermissionRE = ACL_PermissionRE.PadLeft(PaddingValue) & " [" & ACL_Type & "]" Else ACL_PermissionRE = ""

 If ACL_PermissionRE.Trim() <> "" Then ACL_PermissionRE = ACL_PermissionRE.PadLeft(PaddingValue) & " [" & ACL_Type & "]" Else ACL_PermissionRE = ""

        If ACL_PermissionLD.Trim() <> "" Then ACL_PermissionLD = ACL_PermissionLD.PadLeft(PaddingValue) & " [" & ACL_Type & "]" Else ACL_PermissionLD = ""

dim Permissions as String               
Permissions= ACL_PermissionFC & ";" & ACL_PermissionFC & ";" & ACL_PermissionRE & ";" & ACL_PermissionLD & ";" & ACL_PermissionR & ";" & ACL_PermissionW

This way you will see if your string is completely empty or not.

the_lotus · Accepted Answer · 2015-03-10 15:04:09Z

I wouldn't repeat the code. Put it in a function. This could be better with a StringBuilder.

    Dim permissions As String = ""

    permissions = ConcatenateString(permissions, ACL_PermissionFC, PaddingValue, ACL_Type)
    permissions = ConcatenateString(permissions, ACL_PermissionM, PaddingValue, ACL_Type)
    permissions = ConcatenateString(permissions, ACL_PermissionRE, PaddingValue, ACL_Type)
    permissions = ConcatenateString(permissions, ACL_PermissionRE, PaddingValue, ACL_Type)
    permissions = ConcatenateString(permissions, ACL_PermissionLD, PaddingValue, ACL_Type)

Function ConcatenateString(ByVal str As String, ByVal newValue As String, ByVal paddingValue As Integer, ByVal aclType As String) As String

    newValue = newValue.Trim() ' Needed?

    If newValue.Length > 0 Then
        newValue = newValue.PadLeft(paddingValue)

        If str.Length > 0 Then
            str &= ";"
        End If

        str &= String.Format("{0} [{1}]", newValue, aclType)
    End If

    Return str
End Function

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