What is the standard way to implement optional query parameters in a .NET WinForms application?In other words, only query on a field if the value of a corresponding control is not null.
EDIT: I use a FillBy method which calls a query in my Access database. In the TableAdapter query editor, I just used WHERE (field1 = ?) AND (field2 = ?) ... I just can't find the "hook" to bind form controls to the table adapter query parameters and so that if a form uses the default value to not query on it.
However, I am wondering if there are any workarounds or plans for incorporating this feature into VB.NET in the future?What I'd like to do:
Public Delegate Function Deserializer(Of T)(ByRef Buffer() As Byte, optional ByRef BufferPosition As Integer = 0) As T 'Implementation of a func that matches the delegate' Class A Public Function Deserialize(Byref Buffer() as Byte, optional Byref BufferPosition as integer = 0) ....
In the absence of specifying "optional" inside the actual delegate itself, it'd at least be nice to be able to do it in the function implementation only:
Public Delegate Function Deserializer(Of T)(ByRef Buffer() As Byte, ByRef BufferPosition As Integer) As T 'Implementation of a func that matches the delegate' Class A Public Function Deserialize(Byref Buffer() as Byte, optional Byref BufferPosition as integer = 0) ....
At least this second way, the functions for the delegate will always have a value mapped to each parameter, although some may come from the function side and not the calling side.
I tried DbNull.Value but no luck. How do I assign a default value as null to a string parameter that is null in VB.NET? Its litte strange to see that VB does not have anything like plain null as most of the other languages do. Also what is the difference between null and DbNull and Nothing.
I have an object, called 'PERSON' This person object has a title, firstName & Surname property as well as many other which are at the moment irrelevant. It also has a read only property called Fullname which concatenates the two or three parameters mentioned above depending on an optional parameter 'withTitles' passed over when you call PERSON.FULLNAME
PERSON.FULLNAME(true) <- Will add titles if there are any
PERSON.FULLNAME(false) <- Will give the name without the title
Public ReadOnly Property FullName(Optional ByVal withTitle As Boolean = False) As String
[Code]...
I get an error: PERSON does not contain a property of 'FullName'. If I change this to any other property that does not take a parameter it works as expected. Now I'm guessing that the binding procedure can't handle optional or mandatory parameters for object properties, is this right? Is there a better way to do it? I thought about looping through the collection to add them manually but that kinda defeats the object of DataBinding!
I was familiar with the optional parameters in vb 6 and it made sense given the capabilities of the language but why the heck does VB.Net support optional parameters when there is method overloading? Which one should I use and is there a difference? If there is a difference when should I use each one?
I have a custom Attribute class where the constructor takes one fixed parameter and two optional parameters. It is my understanding that one can supply one or more optional parameters by using 'named parameters' such as this:
Private Sub CallMethod() Me.OptionalMethod(-1, z:=1) End Sub
[code]....
Well, I thought, perhaps Attributes don't support named parameters. I know they can behave a little weird (they don't support all types in their arguments for example I think), so I thought little of it.But then... I noticed something else. If you take a look at my code of the attribute class again. Notice that I am using an attribute on that class as well... And what do you know: named parameters. Working just fine... The AttributeUsage attribute has the exact same configuration: one fixed parameter and two optional parameters. I seem to be able to call them using named parameters just fine, where I cannot call my own attribute constructor with named parameters...
Most of our code base is in VB.NET. I'm developing a project in C# that uses a lot of the assemblies from the VB.NET code.There are three relevant classes in VB.NET:
I'm using a stored procedure to updateinsert data into a table using MERGE. One of the items being inserted is a VarBinary file. Now if I wish to add a new file it's just a case of using ReadAllBytes as below, to remove the file I pass DBNull. Now what if other fields are being updated but the file is not being changed? I want the field to remain untouched unless I'm replacing the file or deleting it as above. I cannot add the file via the parameter again as it may only exist in the database, unless I read it first and write it back which seems pointless. [Code]
I have a search function de build.We are using pure ASP.NET w VB.NET We have multiple DropDownLists and we're building a search query with whatever was selected in those DDLs. My question is, how can I handle the blank values (unselected dropdownlist values) with the SQL Query ? I'm using AND operators in the query so if anything is blank it'll fail the search. If the dropdownlist has no selected value, i don't want the value to be part of the search. It would be easy to code with just 2-3 parameters, but we're looking thru at least 10 items and doing a SWITCH CASE or multiple IFs would soon become mayhem.
I have a DataGridView to which I've set a list of objects to the DataSource. (I'm in VS 2005 using VB.) I created the DataGridView by creating a Data Source of type AssetIdentifier and dragging that Data Source onto my form. I want to update the DataGridView when the selection in either a combo box or another DataGridView changes. (Below I'm considering a click in another DataGridView.)
The following works: Public Class dlgShowAssets ' class member variable Private assetIdList As List(Of AssetIdentifier) ' pertinent subs and functions Private Sub RefreshAssetIdentifierDataGridView() [Code] .....
In this case, I always knew that assetIdList would have at least one element. I'd update the list, and reset the data source of the DataGridView to that list, and all was well. When I applied this to another situation, for which I couldn't guarantee that the list would have at least one element, things would work fine as long as I had at least one element in the list, but if the list became empty, the DataGridView threw System.IndexOutOfRangeException a number of times.
The rows in the DataGridView would not go away if I went from a non-zero number of elements to zero. I tried a workaround, which was to remove all of the elements, add one "dummy" element, and then re-bind the list to the control and it still didn't work. Also, following all of those exceptions, I'd get other similar exceptions when I hovered over the cells in the DataGridView. Some of the members of AssetIdentifier were "Nothing" but I fixed that in the constructor, and the exceptions still occur.
I just got upgraded from VB6.0 to VB2010. I'm trying to move some of my program functions over and I'm getting an error on the ones where I use optional... Public Function GetFolder(ByRef FTT As String, Optional InitFile As String)
I get the error at the end of the line, after the close par...the error is "optional parameters must specify a default value".
I am trying to have an optional Date value in one of my sub but since you cant set Date to nothing, this doesn't work. And i cant set it to the Date.minvalue inline.
Private Sub abc (ByVal A As String, Optional ByVal B As Date = Nothing) End Sub
So, i went and set it to some date in the past.
Private Sub abc (ByVal A As String, Optional ByVal B As Date = #1/1/2001#) End Sub
what would be the proper way to handle the default value for an optional Date?
I'm writing a query to select all records that has any part of parameter. I have one table called Employees. Some people have name like this: John David Clark If the parameter is
[Code]....
I should be able to get result back as long as there's a match in the parameters. If I use Function Contains (q.FirstName & " " & q.LastName).Contains(employeeName), I will not get any result back if employeeName is "John Clark" Function Contains looks only for next words from left to right. It doesn't match a single word at a time. So that's why I used this in the Linq to SQL:
I am getting error [07002] the # binded parameters < the # of parameters makers, i checked both parameters were perfect even though i am getting this error here is my code
Basically Commands has Parameters and parameters has functions like Add, AddWithValue, and etc. In all tutorials i've seen, i usually noticed that they are using Add instead of AddWithValue.
[Code]...
since it saves my coding time. So which is better to use? Which is safe to use? Does it improves performance?
is there a way to get the GET parameters and POST parameters in just one function or Collection in ASP.NET? Like using $_REQUEST in PHP? I'm using VB.NET.
I'm trying to convert come vb.net code into C# from another programmers old work but came across optional in one of the functions.[code]...
It seems like instead of using overloading, VB.Net has an option to create it into one method/function. Does C# have a similar equilvalent or do I have to create a method for each possbility?
I have an application that does a search of our database (exposed via EF) for records meeting certain conditions. We have two main tables (Jobs and Recipients). Recipients are linked to the Jobs table by a Job ID.The job record has various fields (Process Date, NameJobType). The recipient has a lot of Name and ID fields (e.g. Account Number, Surname, etc)
I'm looking at an old module to add some new features. I noticed this in a subroutine declaration:sub foo(...,optional fum as integer = 0)the later if not isnothing(fum) then <do something>I'm wondering, will <do something> ever be executed? I'm guessing not, since fum has a default value, but I want to be sure I'm getting this correctly.
I have an application that does a search of our database (exposed via EF) for records meeting certain conditions. We have two main tables (Jobs and Recipients). Recipients are linked to the Jobs table by a Job ID.The job record has various fields (Process Date, Name, JobType). The recipient has a lot of Name and ID fields (e.g. Account Number, Surname, etc)I want to present a search screen where they see a list of fields to search on. The ASP.net code then sees which textboxes the user typed in (or selected), and builds a query based on that. [code] Where I'm stuck is figuring out how to add in additional where clauses. Should I just use Entity SQL?Can this return strongly typed EF objects as well? And is it possible to return both the Jobs and Recipients objects?
I have a method written in VB.NET. It looks like this:
Shared Sub SomeMethod(ByVal Id As Guid, Optional ByVal str1 As String = "foo", Optional ByVal str2 As String = "")
I want to call this method from C# 3.0 and I want it to use its default arguments. I tried passing System.Reflection.Missing.Value, but I cannot cast it as String. Is there any way to do that?
