In my code I store a string array as an object inside a dictionary. Because that dictionary is a <string,object> type when I retrieve the value from dict like dict.item("string") it gives me only an object (obviously) but I need a string array. How to take it back now ?
I have seen many questions here,
they are like object array to string array, some are same of mine but in java, I need a one line code in Vb.net
edit :
code which stores the string array in to the dictionary
string_array[2] = {username, new system.Net.NetworkCredential(string.Empty, password).Password} ; out_Config(row("Name").ToString) = string_array
If you can't modify the dictionary to hold string arrays instead of objects (because it also holds other types) then you can cast the values back to string arrays from objects:
Dim dict As New Dictionary(Of String, Object)
dict.Add("item", New String() {"1", "2"})
Dim stringArray = CType(dict("item"), String())
Related
Needed code is something like this:
Dim myArray(0) As String
Dim ay As String = "ay"
myArr & ay(0) = "asd"
I've tried but did not worked
Dim classlist1(0) As String
Dim classlist2(0) As String
Dim classlist3(0) As String
Dim classlist4(0) As String
Dim count As Integer = 0
For _year As Integer = 1 To 4
("classlist" & _year)(count) = "hi"
count += 1
Next
Any time you see something like this:
Dim classlist1(0) As String
Dim classlist2(0) As String
Dim classlist3(0) As String
' etc.
It's an indication that you're using the wrong data structure. Instead of trying to dynamically build variable names (which isn't really possible in a static language, at least not without some really ugly reflection code with a high potential for runtime errors), just use a collection.
For example, if you want a collection of strings:
Dim classList As New List(Of String)()
And if you want a collection of collections of strings:
Dim classLists As New List(Of List(Of String))()
Then you can reference the nested lists within the parent list. So to add your first "year" of classes:
classLists.Add(new List(Of String))
And add a class to that year:
classLists(0).Add("some value")
As you can see, it starts to get a little difficult to keep track of the data structures. This is where creating custom types and structures becomes very useful. For example, rather than representing a "year" as a list of strings, create an actual Year class. That class can internally hold a list of strings, and other logic/data.
Try Dictionary<TKey, TValue> Class From MSDN.
Dim classLists As New Dictionary(Of String, String)()
'Add items with keys
For _year As Integer = 1 To 4
classLists.Add(String.Format("classlist{0}",_year), "hi")
Next
And you can get value by key later
Dim key As String = "classlist2"
Dim value As String = classLists(key)
I am making a LIST to organize and manipulate arrays that represent lines off a spreadsheet. I've created a custom class for the arrays, and will call them out as objects.
My question is, can I use a value stored in a variable as the name of the object? If so, what would the syntax look like?
dim FileName as String
FileName = 123456.csv
Public Class List_Array
public variable1 as string
public variable2 as string
public variable3 as string
public variable4 as string
End Class
dim File_Name as List_Array = NEW List_Array
This is the coding as I understand it, but I keep thinking this will only create one Object over and over again with the same name as the string variable.
If not, how can I differentiate the different objects as I call them? There will be thousands of objects to reference, so using an unnamed object will not work so well.
If you want to store a list of named objects, what you need is a Dictionary. Dictionary objects store a list of key/value pairs. In this case, the "key" is the name that you want to assign to the object, and the value is the reference to the object itself. It's a generic class, which means when you use the Dictionary type, you must specify the types that you want it to use for it's keys and values. For instance Dictionary(Of String, MyClass) will create a list that uses String objects for its keys and MyClass objects for its values.
Here's an example of how you could use a dictionary to store a list of people with their ages:
Dim d As New Dictionary(Of String, Integer)()
d("Bob") = 30
d("Mary") = 42
Then, when you want to read a value, you can do it like this:
Dim age As Integer = d("Bob")
The Dictionary will only allow one item per key. It uses a hash table to index the values by their keys, so it's very fast get any item by its key.
Edit
Based on your comments below, here's a more pertinent example to show what I mean. Let's say you have a CSV file containing a list of people. So you create a class that stores all of the information about one person (one line of the CSV file), like this:
Public Class Person
Public Property Id As String
Public Property Name As String
Public Property Title As String
End Class
Then, you create a method which parses a single line from the CSV file and returns all of the fields from that line as an array of strings, like this:
Public Function ParseCsvLine(line As String) As String()
' ...
End Function
Then, you could load all of the people into a list, like this:
Dim persons As New List(Of Person)()
For Each line As String In File.ReadAllLines("People.csv")
Dim fields() As String = ParseCsvLine(line)
Dim person As New Person()
person.Id = fields(0)
person.Name = fields(1)
person.Title = fields(2)
persons.Add(person)
Next
Now you have all of the Person objects loaded into one list. The problem is, though, that the list is not indexed. If, for instance, you needed to find the person with an ID of 100, you'd need to loop through all of the Person objects in the list until you found one with that value in it's Id property. If you want to index them by ID so that you can find them more easily/quickly, you can use a Dictionary, like this:
Dim persons As New Dictionary(Of String, Person)()
For Each line As String In File.ReadAllLines("People.csv")
Dim fields() As String = ParseCsvLine(line)
Dim person As New Person()
person.Id = fields(0)
person.Name = fields(1)
person.Title = fields(2)
persons(person.Id) = person
Next
Then, when you need to get a person from the dictionary, you can easily access it by ID, like this:
Dim person100 As Person = persons("100")
I have to read data from database to multidimensional array of unknown size.
Dim myarray As String()
Using reader = mcmd.ExecuteReader()
While (reader.Read())
myarray = TryCast(reader("mydataarray"), String())
End While
End Using
Here I got in myarray array of strings of last readed row only.
How to get that in 'myarray' will be readed data of all rows from sql result?
Here is code to do what I think you mean:
Using reader = mcmd.ExecuteReader()
Dim myOuterList as New List(of String())
While (reader.Read())
Dim myInnerList as New List(of String)
'For loop retrieves all columns of data as string
For i = 0 to reader.FieldCount - 1
myInnerList.Add(reader.GetString(i))
Next
myOuterList.Add(myInnerList.ToArray)
End While
End Using
dim myarray = myOuterList.ToArray
Resulting myarray will be of type String()() I.E. a two-dimensional array of strings.
Though this is possible, I would seriously consider using a typed solution as it will be much easier to understand code dealing with a list of a type than a two-dimensional array.
The typed version would be something like this:
Dim myList As List(Of myType) = reader.OfType(Of IDataRecord) _
.Select(Function(data) New myType _
With {.mydataarray = data.item("mydataarray")})
'Additionaly properties if needed.
The code I have is:
Dim Dbase() As String = Nothing
Dbase(0) = Db_ComboBox.Text
I have declared Dbase as array and assigned Nothing, Db_ComboBox is a combobox.
For that assignment statement, I'm getting the following error: "Reference 'Dbase' has a value of 'Nothing'"
What is the reason for this error, and how can I take the value from the combobox and save it in the array?
You need to change this:
Dim Dbase() As String = Nothing
to this (declare an array of 1 element):
Dim Dbase(0) As String
And then this line will work:
Dbase(0) = Db_ComboBox.Text
If you need to change your array size you can use Redim or Redim preserve, as required.
If you anticipate contents of Dbase to change often, I am all with #Joel's suggestion about switching to List(Of String) instead of handling array sizes manually.
Let's look at your code:
Dim Dbase() As String = Nothing
Dbase(0) = Db_ComboBox.Text
Especially the first line. That first line creates a variable that can refer to an array, but the = Nothing portion explicitly tells it, "Do not create a real array here yet". You have, effectively, a pointer that doesn't point to anything.
I get here that what you really need is a List collection that you can append to over time:
Dim Dbase As New List(Of String)()
Dbase.Add(Db_ComboBox.Text)
Dbase() IS NOTHING. Look at this example:
cargoWeights = New Double(10) {}
atmospherePressures = New Short(2, 2, 4, 10) {}
inquiriesByYearMonthDay = New Byte(20)()() {}
That's how you declare arrays.
More examples: http://msdn.microsoft.com/en-us/library/vstudio/wak0wfyt.aspx
I have a ComboBox which I assign to a variable:
Dim var as String = ComboBox1.SelectedValue
Dim name As String = var.Split(",")
This gives me the error
Value of type '1-dimensional array of string' cannot be converted to String
Any ideas as to where I'm going wrong?
Split returns an array of strings. Your variable needs to be changed to an array, not just a single string.
My VB is a bit rusty, but I think you have to make name an array:
Dim name() As String = var.Split(",")
name needs to be declared as an array.
dim name() as string = var.split(",")
The split() method will break up the string based on the given character and put each newly created string into an array and return it.
This is what your error message is telling you:
Value of type '1-dimensional array of string' cannot be converted to String
The method returns an array of string, but your trying to put it into just a string!
EDIT: In response to your answer...
So far you've managed to split the string yourself with the split method. To output this to your message box, you need to concatenate the two elements in the proper order:
msgbox(name(1) & " " & name(0))
Notice I indexed the array twice! Element 1 is the first name, element 0 is the last name. Remember you got this name in lname,fname format. Passing the array itself doesn't make sense! Remember, a datatype is not equal to an array of that type, they are two different things. Therefore a string is not compatible with a string array. However, each individual element of the array is a string, and so each of those are compatible with the string type (because they're the same thing)!
Dim var As String = ComboBox1.SelectedValue
Dim temp() As String = Split(var, ",", -1, CompareMethod.Binary)
Dim name As String = temp(0)
Or maybe "name" isn't an array and the goal is to populate "name" with everything up until the first comma, in which case the fix would be:
Dim name as String = var.Split(",")(0)
Note: assumes that var is not Nothing.