I have a for each loop in vb.net for this particular example there are 2 items in list but after the first item the loop exits are there errors in the code
Public Function findUserID(ByVal list As List(Of KeyValuePair(Of String, String)), ByVal value As String)
Dim id As String = String.Empty
For Each kvp In list
If (kvp.Value = value) Then
id = kvp.Key
End If
Next
Return id
End Function
Try to use this:
dim kvp as KeyValuePair
kvp = list.Find(p=>p.Value = value))
if kvp = null then return "" else return kvp.Key
One user told me to modify it in this way:
dim kvp = list.Find(Function(e) e.Value = value)
If kvp Is Nothing Then Return "" Else Return kvp.Key
Sorry if this code has some error, but I cannot try and I usually write in C#.
So my code (in C#) would be:
KeyValuePair kvp = list.Find(p=>p.Value == value));
return kvp == null ? "" : kvp.Key;
Why you have the id variable and don't return the Key directly if you found a valid?
So the collection will loop through all KeyValuePairs and not stop on any results.
Public Function FindUserID(ByVal list As List(Of KeyValuePair(Of String, String)), ByVal value As String)
For Each kvp In list
If (kvp.Value = value) Then
Return kvp.Key
End If
Next
End Function
But thats not the error, did you debug the method and verified that there are more than one KeyValuePairs in the list?
Related
I have a KeyValuePair(Of TKey,TValue) and I want to check if it is null or not:
Dim dictionary = new Dictionary(Of Tkey,TValue)
Dim keyValuePair = dictionary.FirstOrDefault(Function(item) item.Key = *someValue*)
If keyValuePair isNot Nothing Then 'not valid because keyValuePair is a value type
....
End If
If keyValuePair <> Nothing Then 'not valid because operator <> does not defined for KeyValuePair(of TKey,TValue)
...
End If
How can I check if keyValuePair is null or not?
KeyValuePair(Of TKey, TValue) is a struct(Structure), it has default value which you can compare to.
Dim dictionary As New Dictionary(Of Integer, string)
Dim keyValuePair = dictionary.FirstOrDefault(Function(item) item.Key = 2)
Dim defaultValue AS KeyValuePair(Of Integer, string) = Nothing
If keyValuePair.Equals(defaultValue) Then
' Not found
Else
' Found
End If
Nothing represents default value of the corresponding type.
But because you are searching Dictionary for a key, you can use TryGetValue instead
Dim dictionary As New Dictionary(Of Integer, string)
Dim value As String
If dictionary.TryGetValue(2, value) Then
' Found
Else
' Not found
End If
I have a problem when I use .count in my 2D String list. This is the code:
If File.Exists(fullPath) = True Then
Dim readText() As String = File.ReadAllLines(fullPath)
Dim s As String
accountCounter = 0
For Each s In readText
accountList.Add(New List(Of String))
accountList.Add(New List(Of String))
accountList.Add(New List(Of String))
accountList(accountCounter).Add(s.Split(",")(0))
accountList(accountCounter).Add(s.Split(",")(1))
accountList(accountCounter).Add(s.Split(",")(2))
accountCounter += 1
Next
print_logs(accountList.count)
End If
The result is this:
{{name,email,password},{name2,email2,password2},{name3,email3,password3},{name4,email4,password4}}
beacuse in the file there are the following lines:
name,email,password
name2,email2,password2
name3,email3,password3
name4,email4,password4
But data is not the problem, the real problem is the Count method, it returns (12). I think that it returns 4 * 3 result, because if I add this in the code:
print_logs(accountList(0).Count)
it correctly returns 3.
So, how can I just return 4?
In this code you create three new rows everytime you do an iteration... If there are four lines in your text files then you will create twelve...
Do this instead :
If File.Exists(fullPath) = True Then
Dim readText() As String = File.ReadAllLines(fullPath)
Dim s As String
accountCounter = 0
For Each s In readText
accountList.Add(New List(Of String))
accountList(accountCounter).Add(s.Split(",")(0))
accountList(accountCounter).Add(s.Split(",")(1))
accountList(accountCounter).Add(s.Split(",")(2))
accountCounter += 1
Next
print_logs(accountList.count)
End If
And if you want to make it even better :
If File.Exists(fullPath) = True Then
Dim readText() As String = File.ReadAllLines(fullPath)
For Each s As String In readText
Dim newList = New List(Of String)
newList.Add(s.Split(",")(0))
newList.Add(s.Split(",")(1))
newList.Add(s.Split(",")(2))
accountList.Add(newList)
Next
print_logs(accountList.count)
End If
I have a problem...
I am trying to put into a list of String dictionary keys values if condition of containsvalue is true:
But, this is not correct :(
here is a code:
Private listID As New List(Of String) ' declaration of list
Private dictionaryID As New Dictionary(Of String, Integer) ' declaration of dictionary
'put a keys and values to dictionary
dictionaryID.Add("first", 1)
dictionaryID.Add("second", 2)
dictionaryID.Add("first1", 1)
If dictionaryID.ContainsValue(1) Then ' if value of dictinary is 1
Dim pair As KeyValuePair(Of String, Integer)
listID.Clear()
For Each pair In dictionaryID
listID.Add(pair.Key)
Next
End If
And now, list must have two elements... -> "first" and "first1"
Can you help me?
Thank you very much!
You are looping through the whole dictionary and add all the elements to the list. You should put an if statement in the For Each or use a LINQ query like this:
If listID IsNot Nothing Then
listID.Clear()
End If
listID = (From kp As KeyValuePair(Of String, Integer) In dictionaryID
Where kp.Value = 1
Select kp.Key).ToList()
Using an if statement:
listID.Clear()
For Each pair As KeyValuePair(Of String, Integer) In dictionaryID
If pair.Value = 1 Then
listID.Add(pair.Key)
End If
Next
My VB.Net is a little rusty, but it looks like you were adding all of them, no matter if their value was 1 or not.
Private listID As New List(Of String) ' declaration of list
Private dictionaryID As New Dictionary(Of String, Integer) ' declaration of dictionary
'put a keys and values to dictionary
dictionaryID.Add("first", 1)
dictionaryID.Add("second", 2)
dictionaryID.Add("first1", 1)
If dictionaryID.ContainsValue(1) Then ' if value of dictinary is 1
Dim pair As KeyValuePair(Of String, Integer)
listID.Clear()
For Each pair In dictionaryID
If pair.Value = 1 Then
listID.Add(pair.Key)
End If
Next
End If
I know I can do this with a for loop cause that's how i'm doing it now. I was hoping for a more efficient way to accomplish the task.
I have a dictionary(Of Integer, Boolean)
or Of String, Boolean.
i want to get a list(of integer) or Of String from the dictionary where all the values are true(or false depending on what i need at the time)
and to generalize it or "black box" it, it could be any dictionary(of whatever, whatever)
and return a list(of whatever) where the value = whatever i'm looking for at the time.
string, string where value = "Closed"
in short: i want all list of all the keys who's value = some criteria
my current code:
Public Function FindInDict(Of tx, ty)(thedict As Dictionary(Of tx, ty), criteria As ty) As List(Of tx)
Dim tmpList As New List(Of tx)
For xloop As Integer = 0 To thedict.Count - 1
If CType(thedict(thedict.Keys(xloop)), ty).Equals(criteria) Then
tmpList.Add(thedict.Keys(xloop))
End If
Next
Return tmpList
End Function
You can do this easily with Linq:
Public Function FindInDict(Of tx, ty)(thedict As Dictionary(Of tx, ty), criteria As ty) As List(Of tx)
Return (From kvp In thedict
Where kvp.Value.Equals(criteria)
Select kvp.key).ToList()
End Function
Use LINQ, like so:
Dim tStorage As Dictionary(Of String, String) = New Dictionary(Of String, String)
Dim tKeys As List(Of String) = New List(Of String)
Dim tCriteria As List(Of String) = New List(Of String)
tStorage.Add("One", "Uno")
tStorage.Add("Two", "Dos")
tStorage.Add("Three", "Tres")
tStorage.Add("Four", "Quatro")
tCriteria.Add("Dos")
tCriteria.Add("Quatro")
tKeys = (From k In tStorage.Keys Where tCriteria.Contains(tStorage(k)) Select k).ToList
For Each tKey As String In tKeys
Console.WriteLine(tKey)
Next
Console.ReadKey()
In VB.NET, how can I convert the following string into some kind of key/value type such as a Hashtable, Dictionary, etc?
"Name=Fred;Birthday=19-June-1906;ID=12345"
I want to extract Birthday or ID without having to split the string into an array.
EDIT: I'd prefer not to split the string into an array in case the format of the string changes later. I don't have control over the string. What if someone switches the order around or adds another element?
I’m currently unable to test this, lacking a VB compiler, but the following solution should also work, and it has the advantage of not requiring an explicit loop. It uses the Linq method ToDictionary and two nested Split operations:
Dim s = "Name=Fred;Birthday=19-June-1906;ID=12345"
Dim d = s.Split(";"c).Select(Function (kvp) kvp.Split("="c)) _
.ToDictionary( _
Function (kvp) kvp(0), _
Function (kvp) kvp(1))
First, we split on the outer delimiter (i.e. the semi-colon). From the resulting array, we select by splitting again, this time on =. The resulting array of arrays is converted to a dictionary by specifying that the first item is to become the key and the second is to become the value (the identifier kvp stands for “key-value pair”).
Since I can’t check the exact VB syntax and the above may contain subtle errors, here is the equivalent C# code (tested for correctness):
var s = "Name=Fred;Birthday=19-June-1906;ID=12345";
var d = s.Split(';').Select(kvp => kvp.Split('='))
.ToDictionary(kvp => kvp[0], kvp => kvp[1]);
Not sure why you don't want to split it. If you're sure there won't be any extra = or ; then you could just do:
Dim s As String = "Name=Fred;Birthday=19-June-1906;ID=12345"
Dim d As New Dictionary(Of String, String)
For Each temp As String In s.Split(";"c)
Dim index As Int32 = temp.IndexOf("="c)
d.Add(temp.Substring(0, index), temp.Substring(index + 1))
Next
Which might not be beautiful, but is very easy to understand.
input.Split(";"c) returns an array of key/value:
{ "Name=Fred", "Birthday=19-June-1906" , "ID=12345" }
so pair.Split("="c) returns { "Name", "Fred" } etc
If you want an alternative to doing a String.Split; there is always Regular Expressions as an alternative:
Dim map As Dictionary(Of String, String) = New Dictionary(Of String, String)
Dim match As Match = Regex.Match("Name=Fred;Birthday=19-June-1906;ID=12345", "(?<Name>[^=]*)=(?<Value>[^;]*);?")
While (match.Success)
map.Add(match.Groups("Name").Value, match.Groups("Value").Value)
match = match.NextMatch()
End While
The regular expression itself could be beefed up to better handle whitespace between key/value's and pair's but you hopefully get the idea. This should only pass through the string once to build up a string dictionary of keys and values.
Dim persSeparator as string=";"
Dim keyValSeparator as string="=";
Dim allPersons As New Dictionary(Of String, Person)
Dim str As String = "Name=Fred;Birthday=19-June-1906;ID=12345"
Dim parts As New List(Of String)(str.Split(persSeparator.ToCharArray)) 'why dont want you to split this string??
Dim person As New Person
For Each part As String In parts
Dim keyValue() As String = part.Split(keyValSeparator.toCharArray())
Select Case keyValue(0).ToUpper
Case "ID"
person.ID = keyValue(1)
Case "NAME"
person.Name = keyValue(1)
Case "BIRTHDAY"
person.BirthDay= keyValue(1)
End Select
Next
If Not allPersons.ContainsKey(person.ID) Then
allPersons.Add(person.ID, person)
End If
Public Class Person
Private _name As String
Private _birthday As String
Private _id As String = String.Empty
Public Sub New()
End Sub
Public Sub New(ByVal id As String)
Me._id = id
End Sub
Public Sub New(ByVal id As String, ByVal name As String)
Me._id = id
Me._name = name
End Sub
Public Sub New(ByVal id As String, ByVal name As String, ByVal birthday As String)
Me._id = id
Me._name = name
Me._birthday = birthday
End Sub
Public Property ID() As String
Get
Return Me._id
End Get
Set(ByVal value As String)
Me._id = value
End Set
End Property
Public Property Name() As String
Get
Return Me._name
End Get
Set(ByVal value As String)
Me._name = value
End Set
End Property
Public Property BirthDay() As String
Get
Return Me._birthday
End Get
Set(ByVal value As String)
Me._birthday = value
End Set
End Property
Public Overrides Function Equals(ByVal obj As Object) As Boolean
If TypeOf obj Is Person AndAlso Not obj Is Nothing Then
Return String.Compare(Me._id, DirectCast(obj, Person).ID) = 0
Else : Return False
End If
End Function
End Class
If you were just wanting to extract the birthday and ID from the string and place as a value pair in some sort of dictionary, for simplicity I would use regular expressions and then a generic dictionary (of string, valuepair structure). Something like this:
Imports System.Text.RegularExpressions
Imports System.Collections.Generic
Sub Main()
Dim Person As New Dictionary(Of String, ValuePair)
Dim s As String = "Name=Fred;Birthday=19-June-1906;ID=12"
Dim r As Regex = New Regex("Name=(.*);Birthday=(.*);ID=(.*$)")
Dim m As Match = r.Match(s)
Person.Add(CStr(m.Groups(1).Value), _
New ValuePair(CDate(m.Groups(2).Value), CInt(m.Groups(3).Value)))
Console.WriteLine(Person("Fred").Birthday.ToString)
Console.WriteLine(Person("Fred").ID.ToString)
Console.Read()
End Sub
Friend Structure ValuePair
Private _birthday As Date
Private _ID As Int32
Public ReadOnly Property ID() As Int32
Get
Return _ID
End Get
End Property
Public ReadOnly Property Birthday() As Date
Get
Return _birthday
End Get
End Property
Sub New(ByVal Birthday As Date, ByVal ID As Int32)
_birthday = Birthday
_ID = ID
End Sub
End Structure