I have a Dictionary object declared as var as Dictionary(of String, String).
I am trying to utilize the LINQ extensions available to the Generic Collection but am only getting the non-extension methods.
I need to turn the Dictionary collection into a string with the following pattern: key1=val1, key2=val2, ..., keyn=valn
Thought at first doing a foreach loop would hit the spot except the fact that i am programmers-block.
What i have so far, but doubt its the best logic pattern for producing this:
Public Overrides Function ToString() As String
Dim ret As String = ""
For Each kv As KeyValuePair(Of String, String) In Me._set
If ret <> String.Empty Then
ret &= ", "
End If
ret &= String.Format("{0}={1}", kv.Key, kv.Value)
Next
Return ret
End Function
And for some reason even though i have imported the System.Core & System.Linq libraries into the project none of the extended LINQ extensions are showing up in my dev-env intellisense. So for now, unless someone could help me get the LINQ extensions to show up in Intellisense, they are out of the question.
Found the problem with the LINQ extensions not showing up, so they are back on the table ;)
I would have written the whole method block with Linq like this (sorry for the C#-vb.net soup...)
c-sharp
return String.Join(",",Me._set.Select(kvp=>String.Format("{0}={1}",kvp.Key, kvp.Value).ToArray());
Also, I don't really know what _set is. Maybe you'll have to cast :
c-sharp:
return String.Join(",", Me._set.Cast<KeyValuePair<String,String>>().Select(kvp=>String.Format("{0}={1}",kvp.Key, kvp.Value).ToArray());
vb.net:
return String.Join(", ", Me.Select(Function(kvp) String.Format("{0}={1}", kvp.Key, kvp.Value)).ToArray())
Hope this will help,
As far as your non-LINQ loop goes, I would recommend doing it like this:
Public Overrides Function ToString() As String
Dim items As New List(Of String)(_set.Count)
For Each pair As KeyValuePair(Of String, String) In _set
items.Add($"{pair.Key}={pair.Value}"))
Next
Return String.Join(", ", items)
End Function
With LINQ, you could do it like this:
Public Overrides Function ToString() As String
Return String.Join(", ", _set.Select(Function(pair) $"{pair.Key}={pair.Value}"))
End Function
VB.net syntax:
Dim dic As New Dictionary(Of String, String)() From {
{"a", "1"},
{"b", "2"},
{"c", "3"},
{"d", "4"}
}
Dim s As String = String.Join(",", dic.Select(Function(pair) String.Format("{0}={1}", pair.Key, pair.Value)).ToArray())
Related
I am trying to use a LINQ query to grab some data from a database, and since I am grabbing just one column of data I want to store it within a string list. This is the code I have.
Dim POList As New List(Of String)
Using dbContext As New DBLINQDataContext
Dim query = (From o In dbContext.Orders
Where o.Order_Number.StartsWith(JobNumber)
Select o.Order_Number)
POList = query.ToList()
End Using
MessageBox.Show(POList.ToString())
When I run this the data in the MessageBox is
System.Collections.Generic.List`1[System.String]
There is no table data, even though I know there are actual data points for me to be getting :\
POList.ToString() will display the name of the object type.
You can use string.Join(",", POList.ToString()).
You can also define an extension method StringJoin() to show your list as string if you are going to use it frequently.
Here is an extension method that you can use:
public static StringExtensions
{
public static string StringJoin(this IEnumerable<string> strings, string seperator)
{
if (strings == null) return null;
return string.Join(seperator, strings);
}
}
Since this was a vb.net question, I translated #vendettamit 's excellent answer for the benifit of future vb readers.
Public Module StringExtensions
<Extension()>
Public Function StringJoin(MyStrings As IEnumerable(Of String), separator As String) As String
If MyStrings Is Nothing Then
Return Nothing
Else
Return String.Join(separator, MyStrings)
End If
End Function
End Module
To use the extension...
Dim l As New List(Of String) From {"Mathew", "Mark", "Luke", "John"}
Dim s As String = l.StringJoin(", ")
Debug.Print(s)
I'm trying to split a string into a list of strings with this vb.net code, while adding it to a dictionary of String:
objevt.wbStr.Add(b, objevt.metalbelowwidth.Item(b).Split({",","-"}).ToList)
But I get an error saying "Value of '1-dimentitional arrary of string' cannot be converted to 'Char' "
If I try to implement splitting with just the comma, it works fine. So the following code works.
objevt.wbStr.Add(b, objevt.metalbelowwidth.Item(b).Split(",").ToList)
But I really want to split the string with two conditions. Any help is appreciated. Thanks!
One of the overloads of the Split Method that takes a String array also needs to have a StringSplitOption parameter also set.
objevt.wbStr.Add(b, objevt.metalbelowwidth.Item(b).Split(New String() {",", "-"}, StringSplitOptions.None).ToList)
Sub Main()
Dim myString As String = "H,c,J-Hello-World"
Dim myList As List(Of String) = New List(Of String)
myList = myString.Split(New String() {"-", ","}, StringSplitOptions.None).ToList
For Each s As String In myList
Console.WriteLine(s)
Next
Console.ReadLine()
End Sub
You need to use the overloaded Split method with an array of char as the separators, like so:
objevt.metalbelowwidth.Item(b).Split(New [Char]() {","c, "-"c })
Demo here
I am simply trying to spit out a string which aggregates a List's values into a NewLine delimited string.
<Extension()>
Public Function ToColumn(Of T)(ByVal source As IEnumerable(Of T)) As String
' assuming Aggregate(Of String) will be inefficient, using StringBuilder
Dim sb As New StringBuilder()
For Each val As T In source
sb.Append(val.ToString() & Environment.NewLine)
Next
Return sb.ToString()
End Function
This method will help while debugging to see the entire contents of a List, while ?source only spits out the first 100 elements in the immediate window (maybe there is a different way to do this?). I just want to be able to copy it over to something like Excel quickly for analysis.
The problem is that although this method compiles, in usage, it is not recognized as an extension of List(of T) i.e.
Dim result As Int32()
Debug.Print(result.ToList().ToColumn())
' this line doesn't compile:
' 'toColumn' is not a member of 'System.Collections.Generic.List(Of Integer)'
I'd like to reuse this method on anything which I can box into an Object and get .ToString() (everything!), hence the generic aspect of it. I have seen many people add constraints to the generic T, i.e. Where T : Constraint, but my constraint would be Object, as is the nature of this method, which doesn't compile.
My question is why isn't it recognized as an extension of List(Of Integer). Also, is what I want to achieve possible?
Have you tried using an extension method on List(Of T) instead of IEnumerable(Of T), like this:
<Extension()>
Public Function ToColumn(Of T)(ByVal source As List(Of T)) As String
' assuming Aggregate(Of String) will be inefficient, using StringBuilder
Dim sb As New StringBuilder()
For Each val As T In source
sb.Append(val.ToString() & Environment.NewLine)
Next
Return sb.ToString()
End Function
I am having trouble understanding the difference between these two commands that in my mind should do the same thing. I have posted the entire code below in case anything is unclear.
I have created two functions in class Person, one that returns a list containing first,middle and last names and one that returns a concatenated string of the name. I reference the function that returns the list to concatenate the string with the line below:
FullName = String.Join(" ", Me.Get_NameList())
However, when I call:
Console.WriteLine(Person1.Print_Name())
I get what looks like the list object instead of the string:
System.Collections.Generic.List`1[System.String]
If I change the code to look like this:
Public Function Print_Name()
Dim FullNameList As List(Of String) = Me.Get_NameList()
Dim FullName As String
FullName = String.Join(" ", FullNameList)
Return FullName
End Function
The console prints:
John Q Doe
Why am I getting a different answer by first assigning the list to a variable and then joining it? Does this have something to do with how the list is stored in memory?
Thanks in advance for the help.
Here is the full code:
Imports System
Module Module1
Sub Main()
Dim Person1 As New Person("John", "Q", "Doe")
Console.WriteLine("Get_Name Values")
Dim g1 As List(Of String) = Person1.Get_NameList()
Console.WriteLine(String.Join(" ", g1))
Console.WriteLine("Print_Name Values")
Console.WriteLine(Person1.Print_Name())
End Sub
End Module
Class Person
Private FirstName As String
Private MiddleName As String
Private LastName As String
Public Sub New(ByVal Fn As String, ByVal Mn As String, ByVal Ln As String)
FirstName = Fn
MiddleName = Mn
LastName = Ln
End Sub
Public Function Get_NameList()
Dim NameList As New List(Of String)
NameList.Add(FirstName)
NameList.Add(MiddleName)
NameList.Add(LastName)
Return NameList
End Function
Public Function Print_Name()
'Dim FullNameList As List(Of String) = Me.Get_NameList()
Dim FullName As String
FullName = String.Join(" ", Me.Get_NameList())
Return FullName
End Function
End Class
GetNameList returns an Object (because you don't specify the return type).
So the Join method is getting an object. So the VB.Net is turning the Object into a String() with one element that is Object.ToString(). Sometimes the method, especially if it is an old school VB holdover, would check to see if the object passed was an IEnumerable and just iterate over the Objects in the passed object. But not always. So having Strict and Explicit OFF can lead to very strange and hard to find bugs. Those two things should only be OFF in very specific cases where you want all the flexibility turning them off gives you AND you are ready to deal with the oddities that result.
Change the return type of Get_NameList to List(Of String)
And turn on option Strict ON and Option Explicit On to see your other problems.
if you change this line:
Public Function Get_NameList()
to
Public Function Get_NameList() AS List(Of String)
And this line
Public Function Print_Name()
to
Public Function Print_Name() as string
it will work
I wrote this - very simple - function, and then wondered does VB have some pre-built functionality to do this, but couldn't find anything specific.
Private Shared Function MakeArray(Of T)(ByVal ParamArray args() As T) As T()
Return args
End Function
Not so much to be used like
Dim someNames() as string = MakeArray("Hans", "Luke", "Lia")
Because this can be done with
Dim someNames() as string = {"Hans", "Luke", "Lia"}
But more like
public sub PrintNames(names() as string)
// print each name
End Sub
PrintNames(MakeArray("Hans", "Luke", "Lia"))
Any ideas?
Any reason not to do:
Dim someNames() as string = New String(){"Han", "Luke", "Leia"}
The only difference is type inference, as far as I can tell.
I've just checked, and VB 9 has implicitly typed arrays too:
Dim someNames() as string = { "Han", "Luke", "Leia" }
(This wouldn't work in VB 8 as far as I know, but the explicit version would. The implicit version is necessary for anonymous types, which are also new to VB 9.)
Dim somenames() As String = {"hello", "world"}
The following codes will work in VB 10:
Dim someNames = {"Hans", "Luke", "Lia"}
http://msdn.microsoft.com/en-us/library/ee336123.aspx
PrintNames(New String(){"Hans", "Luke", "Lia"})
Microsoft recommends the following format
Dim mixedTypes As Object() = New Object() {item1, item2, itemn}
per http://msdn.microsoft.com/en-US/library/8k8021te(v=VS.80).aspx
Note, you don't have to specify the size of new Array, as that is inferred from the initialized count of args. If you do want to specify the length, you specify not the "length" but index number of last space in array. ie. New Object(2) {0, 1, 2} ' note 3 args.