given two lists of the same length, I need to zip the two of them together into a dictionary. I know this can be done using looping but didn't particularly want to go that route. I've seen a few other solutions Map two lists into a dictionary in c# but nothing in VB and I'm having a bit of trouble porting it to VB.NET.
After reviewing the MSDN on iEnumerable.Zip and the referenced solution above, I have the partial solution below. I am struggling implementing the .toDictionary portion. Sample input for each list and current code is below along with current output and desired output.
I am working in a legacy system targeting .Net 4.0
Public Shared sub Main()
Dim headers As Object() = {"key1", "key2", "key3"}
Dim recordData As Object() = {"value1", 2, "value3"}
Dim ziperator = headers.Zip(recordData,
Function(h, r) New With {h, r}).ToDictionary(Function(x) x.r)
End Sub
'Current output:
ziperator = {
["key1",{"key1","value1"}],
["key2",{"key2",2}],
["key3",{"key3","value3"}]
}
'Desired output:
ziperator = {
["key1","value1"],
["key2", 2],
["key3","value3"]
}
Note that the C# version you linked to has two =>s, so:
Dim ziperator = headers.Zip(recordData,
Function(h, r) New With {h, r}).
ToDictionary(Function(q) q.h, Function(q) q.r)
Related
I'd like to convert an unknown basic structure to an Object (no type here).
I'm building a library that will be used by many users to extract data from my system but don't want to do a new function for everyone of them. They have to know what will be the result.
In vb, it is possible to create an Object with some properties and use it as it is a regular Class like so:
Dim myObj as New With { .name = "Matt", .age = "28" }
MsgBox( myObj.name & " is now " & myObj.age & " years old.")
So far, so good.
Next step : my user will give me some instructions that I need to extract data from various DBs, and I've no idea of what the result will be.
What I know after the execution is a list of String containing the columns of the result set and, of course a (set of) rows.
And here is the problem of course
My function (for a single row) so far:
Public Function GetData(ByVal instructions as String) as Object ' User is supposed to know what will be inside, instructions is as XML describing DB, table, query, ...
' Do what is needed to retrieve data
' Here I have a variable cols As List(Of String) ' e.g. ("BP", "NAME", "VAT")
Dim o As New With ???
Return o
End Function
What I've tried: build a fake JSon on the fly, and try to Deserialize to Object.
But even if it seems to work, I (and the user) can't access the property as in my top piece of code like:
MsgBox(o.BP)
I know that I could do
Public Function GetData(Of T As {New})(ByVal instructions as String) As T
Dim o As T
' Use some Reflexion to TryInvokeMember of T
Return o
End Function
But I wanted to remove the hassle to create a class to use my code.
Plus, My librairy will be use in a webservice and the class of the user is then unknown.
One approach could be - to use Dictionary(Of String, Object)
Public Function GetData(instructions as String) As Dictionary(Of String, Object)
Dim data = ' Load data
Dim columns As String() = { "BP", "NAME", "VAT" }
Return columns.ToDictionary(
Function(column) column,
Function(column) data.GetByColumnName(column)
)
End Function
` Usage
Dim result = GetDate("instructions: ['BP', 'NAME']")
' Because user knows it is Integer
Dim bpValue = DirectCast(result.Item("BP"), Integer)
Thanks to #GSerg, #Fabio and a few other searches about ExpandoObject, I did it !
Imports System.Dynamic
Dim o As Object = New ExpandoObject()
For Each col In cols
DirectCast(o, IDictionary(Of String, Object)).Add(col, row.GetString(col))
Next
I've recently implemented reflection to replace the more tedious aspects of our data retrieval from a SQL database. The old code would look something like this:
_dr = _cmd.ExecuteReader (_dr is the SQLDataReader)
While _dr.Read (_row is a class object with public properties)
_row.Property1 = Convert.ToInt16(_dr("Prop1"))
_row.Property2 = Convert.ToInt16(_dr("Prop2"))
_row.Property3 = Convert.ToInt16(_dr("Prop3"))
If IsDBNull(_dr("Prop4")) = False Then _row.Prop4 = _dr("Prop4")
...
Since my code base has a lot of functionality like this, reflection seemed like a good bet to simplify it and make future coding easier. How to assign datareader data into generic List ( of T ) has a great answer that was practically like magic for my needs and easily translated into VB. For easy reference:
Public Shared Function GenericGet(Of T As {Class, New})(ByVal reader As SqlDataReader, ByVal typeString As String)
'Dim results As New List(Of T)()
Dim results As Object
If typeString = "List" Then
results = New List(Of T)()
End If
Dim type As Type = GetType(T)
Try
If reader.Read() Then
' at least one row: resolve the properties
Dim props As PropertyInfo() = New PropertyInfo(reader.FieldCount - 1) {}
For i As Integer = 0 To props.Length - 1
Dim prop = type.GetProperty(reader.GetName(i), BindingFlags.Instance Or BindingFlags.[Public])
If prop IsNot Nothing AndAlso prop.CanWrite Then
props(i) = prop
End If
Next
Do
Dim obj = New T()
For i As Integer = 0 To props.Length - 1
Dim prop = props(i)
If prop Is Nothing Then
Continue For
End If
' not mapped
Dim val As Object = If(reader.IsDBNull(i), Nothing, reader(i))
If val IsNot Nothing Then SetValue(obj, prop, val)
Next
If typeString = "List" Then
results.Add(obj)
Else
results = obj
End If
Loop While reader.Read()
End If
Catch ex As Exception
Helpers.LogMessage("Error: " + ex.Message + ". Stacktrace: " + ex.StackTrace)
End Try
Return results
End Function
The only caveat with this is that it is somewhat slower.
My question is how to optimize. Sample code I find online is all in C# and does not convert neatly into VB. Scenario 4 here seems like exactly what I want, but converting it to VB gives all kinds of errors (Using CodeFusion or converter.Telerik.com).
Has anyone done this in VB before? Or can anyone translate what's in that last link?
Any help's appreciated.
Couple ideas for you.
Don't use the DataReader when reading ALL records at once, it is slower than using a DataAdapter.
When you use the DataAdapter to fill a DataSet, you can iterate through the rows and columns which does NOT use reflection and will be much faster.
I have a program I created (and many other programmers do this too) that generate the code from a database for me. Each table and row is a class that is specifically named an generated in such a way that I can use intellisense and prevents many run-time errors by making them compile-time errors when data changes. This is very much like the EntityFramework but lighter because it fits MY specific needs.
I want to group textframes in my InDesign CS3 vb.net script. It worked for InDesign 2.0 but it does not work with InDesign CS3. Here is my code:
Dim myDoc As InDesign.Document = Nothing
Dim myGroup As InDesign.Group = Nothing
Dim myObjectList(2)
myObjectList.SetValue(myOuterTextFrame, 0)
myObjectList.SetValue(myInnerTextFrame, 1)
myObjectList.SetValue(myContentTextFrame, 2)
myGroup = myDoc.Groups.Add(myObjectList)
Getting error "Unable to cast object of type 'System.Object[]' to type 'InDesign.Objects'."
I know you asked for this a long time ago so I'm mostly answering for future searches. I haven't found a fully managed way to do this using the .Net Framework and believe me, I've searched for it. I've tried a million different casts, subclassing, reflection, you name it. What ultimately worked in the end was JavaScript. Below is a method that takes an InDesign.Document object and two or more integers that represent InDesign item IDs. It then creates some JavaScript and has InDesign execute it. Finally it returns an InDesign.Group created from those objects.
Public Function GroupObjects(ByVal indesignDocument As InDesign.Document, ByVal ParamArray objectIds() As Integer) As InDesign.Group
'Sanity checks
If indesignDocument Is Nothing Then Throw New ArgumentNullException("indesignDocument")
If objectIds Is Nothing OrElse objectIds.Count < 2 Then Throw New ArgumentException("You must pass at least 2 object ids")
'We'll assign a unique label to the group that we create in JavaScript so that we can find it in managed code later
Dim GID = Guid.NewGuid().ToString()
'Create the JavaScript
Dim Buf As New StringBuilder()
Buf.AppendLine("var items = new Array();")
For Each ID In objectIds
Buf.AppendFormat("items.push(app.activeWindow.activePage.pageItems.itemByID({0}));", ID)
Buf.AppendLine()
Next
Buf.AppendLine("var g = app.activeWindow.activePage.groups.add(items);")
Buf.AppendFormat("g.label='{0}';", GID)
Dim IA = indesignDocument.Parent
IA.DoScript(Buf.ToString(), InDesign.idScriptLanguage.idJavascript)
'Loop through all document groups looking for the object with the label created above
For Each G As InDesign.Group In indesignDocument.Groups
If Not String.IsNullOrWhiteSpace(G.Label) AndAlso G.Label = GID Then Return G
Next
Return Nothing
End Function
To use it in your code you'd say:
Dim MyGroup = GroupObjects(myOuterTextFrame, myInnerTextFrame, myContentTextFrame)
This one worked for me:
Type type = Type.GetTypeFromProgID("InDesign.Application");
Host = (InDesign.Application)Activator.CreateInstance(type);
InDesign.Objects o = Host.CreateCollection();
I found my answer in the InDesign Scripting Samples - the Neon sample script gave grouping examples
I'm currently working in .NET 2.0 Visual Basic. The current project is an Active Directory Wrapper class library within which I have a Searcher(Of T) generic class that I wish to use to search the underlying directory for objects.
In this Searcher(Of T) class I have the following methods:
Private Function GetResults() As CustomSet(Of T)
Public Function ToList() As CustomSet(Of T)
Public Function Find(ByVal ParamArray filter() As Object) As CustomSet(Of T)
// And some other functions here...
The one that interests me the most is the Find() method to which I can pass property and values and would like to parse my LDAP query from this filter() ParamArray parameter. Actually, all I can figure out is this:
Public Sub SomeSub()
Dim groupSearcher As Searcher(Of Group) = New Searcher(Of Group)()
Dim groupsSet as CustomSet(Of Group) = groupSearcher.Find("Name=someName", "Description=someDescription")
// Working with the result here...
End Sub
But what I want to be able to offer to my users is this:
Public Sub SomeSub()
Dim groupSearcher As Searcher(Of Group) = New Searcher(Of Group)()
Dim groupsSet As CustomSet(Of Groupe) = groupSearcher.Find(Name = "someName", Guid = someGuid, Description = "someDescription")
// And work with the result here...
End Sub
In short, I want to offer some kind of Expression feature to my users, unless it is too much work, as this project is not the most important one and I don't have like 2 years to develop it. I think that the better thing I should do is to write something like CustomExpression that could be passed in parameters to some functions or subs.
Thanks for any suggestions that might bring me to my goal!
Interesting question. This is a language dependent feature, so I don't see this happening without some clever trickery of the IDE/compiler.
You could however have optional overloads on your Find method (vb.net is good for this), then make the search string manually to obtain the result.
Finally you could make use of lambda functions, but only in .net 3.5 and above. Even still, it would require your searcher to expose a preliminary set of data so you can recover the expression tree and build up the find string.
UPDATE
I've just been playing around with Reflection to see if I can retrieve the parameters passed, and build up a string dynamically depending on if they exist. This doesn't appear to be possible, due to the fact that compiled code doesn't reference the names.
This code just used was:
'-- Get all the "parameters"
Dim m As MethodInfo = GetType(Finder).GetMethod("Find")
Dim params() As ParameterInfo = m.GetParameters()
'-- We now have a reference to the parameter names, like Name and Description
Hmm. http://channel9.msdn.com/forums/TechOff/259443-Using-SystemReflection-to-obtain-parameter-values-dynamically/
Annoyingly it's not (easily) possible to recover the values sent, so we'll have to stick with building up the string in a non-dynamic fashion.
A simple optional method would look like:
Public Sub Find( _
Optional ByVal Name As String = "", _
Optional ByVal Description As String = "")
Dim query As String = String.Empty
If Not String.IsNullOrEmpty(Name) Then
query &= "Name=" & Name
'-- ..... more go here with your string seperater.
End If
End Sub
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.