473,718 Members | 1,955 Online
Bytes | Software Development & Data Engineering Community
+ Post

Home Posts Topics Members FAQ

How to use TypeOf()?

I have a collection that holds DataGridTextBox Column types, which I
then bind to a DataGrid. I loop through all of the
DataGridTextBox Column that were created and add them to the collection
like this

for(int i=0; i<dataGridStyle ColumnCollectio n.Count; i++)

gridTableStyle. GridColumnStyle s.Add((DataGrid TextBoxColumn)d ataGridStyleCol umnCollection[i]);

Sometimes, I'll have a DataGridBoolCol umn, which breaks the above code.
I'm trying to put in a conditional that checks the type. This always
gives a warning:

The given expression is never of the provided
('System.Window s.Forms.DataGri dBoolColumn') type

[the expression]
if(dataGridStyl eColumnCollecti on[i].GetType() is DataGridTextBox Column)

gridTableStyle. GridColumnStyle s.Add((DataGrid TextBoxColumn)d ataGridStyleCol umnCollection[i]);

[In the debugger while looping]
- dataGridStyleCo lumnCollection[i].GetType() {System.Runtime Type} System.RuntimeT ype

+ System.Type {"System.Window s.Forms.DataGri dBoolColumn"} System.Type

The debugger shows it is of the provided type. Neither of the above
conditionals ever run. They always evaluate to false. What does the
compiler and debugger say two different things?

Should I use something else to determine the column type?


Jan 12 '06 #1
1 3283
Brett Romero <ac*****@cygen. com> wrote:
I have a collection that holds DataGridTextBox Column types, which I
then bind to a DataGrid. I loop through all of the
DataGridTextBox Column that were created and add them to the collection
like this
[the expression]
if(dataGridStyl eColumnCollecti on[i].GetType() is DataGridTextBox Column)
The debugger shows it is of the provided type. Neither of the above
conditionals ever run. They always evaluate to false. What does the
compiler and debugger say two different things?

Because what you're asking is whether the type System.Type is an
instance of DataGridTextCol umnBox, which it never is. You're sort of in
a half-way house between:

if(dataGridStyl eColumnCollecti on[i].GetType() ==
typeof(DataGrid TextBoxColumn))


if(dataGridStyl eColumnCollecti on[i] is DataGridTextBox Column)

Either of those would work (although the first one won't "match" if you
give it an instance of something derived from DataGridTextBox Column.

Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too
Jan 12 '06 #2

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

by: Eric | last post by:
I need to do the following but it doesn't compile if(typeof(listBox1.Items) == typeof(string)){ return; } typeof(listBox1.Items) doesn't work at all. My listBox has 2 types of items in them and I need to know what kind of item a user clicked on so I can use it for drag and drop
by: ichor | last post by:
hi what is the use of the typeof keyword , and how does it differ from the GetType method. i found the GetType method useful but i fail to understand the use of the typeof method. i have tried out a very simple example which i made up myself. Employee e = new Employee(); ContractEmp ec =new ContractEmp(); MessageBox.Show(typeof(Employee).ToString());
by: Mark Miller | last post by:
I am using Reflection.Emit to dynamically build a class. A method of the class to be built requires a Parameter of type "Type". But I don't know how to use Emit to pass a call of "typeof()" to the method. The method could look like this: public void myDynamicMethod(Type type){ //.....do something with the Type passed in....... }
by: Alberto | last post by:
Can somebody tell me why this typeof doesn't work? foreach (Control myControl in Controls) if (typeof(myControl) == "TextBox") ((TextBox)myControl).Text = string.Empty; Thank you very much
by: Brien King | last post by:
Ok, I have three classes (The example here is extremely simplified to illustrate the problem) like this: Public Class A Public Sub DoSomething(ByVal myClass) If TypeOf myClass IS A Then ' ' Never Enters here.... ' End If
by: Jason Kendall | last post by:
Why doesn't the new "IsNot" operator work in conjunction with 'Typeof'?
by: Andrew Robinson | last post by:
I am guessing there is a simple solution but given a type T, how can I check for nullability? how can I accomplish the following? bool nullable = typeof(int).IsNullable; // false bool nullable = typeof(int?).IsNullable; // true bool nullable = typeof(string).IsNullable; // true Thanks for any help.
by: EManning | last post by:
Using A2003. I've got an option group that has a number of check boxes. I have coding to clear the option group if the user wishes to cancel their choice. This coding also clears the rest of the controls on the form. Snippet of the coding: <..snipped..> ElseIf TypeOf oCtrl Is CheckBox Then oCtrl.Value = False <..snipped..> ElseIf TypeOf oCtrl Is OptionGroup Then
by: effendi | last post by:
I am testting the following code in firefox function fDHTMLPopulateFields(displayValuesArray, displayOrderArray) { var i, currentElement, displayFieldID, currentChild, nDisplayValues = displayValuesArray.length; for (i=0; i<nDisplayValues; i++) {
by: rkk | last post by:
Hi, Is there an equivalent typeof macro/method to determine the type of a variable in runtime & most importantly that works well with most known C compilers? gcc compiler supports typeof() macro, but the same code is not getting compiled in solaris forte compiler and in microsoft VS 2003 compiler. I tried something like below:
by: marktang | last post by:
ONU (Optical Network Unit) is one of the key components for providing high-speed Internet services. Its primary function is to act as an endpoint device located at the user's premises. However, people are often confused as to whether an ONU can Work As a Router. In this blog post, we’ll explore What is ONU, What Is Router, ONU & Router’s main usage, and What is the difference between ONU and Router. Let’s take a closer look ! Part I. Meaning of...
by: Hystou | last post by:
Most computers default to English, but sometimes we require a different language, especially when relocating. Forgot to request a specific language before your computer shipped? No problem! You can effortlessly switch the default language on Windows 10 without reinstalling. I'll walk you through it. First, let's disable language synchronization. With a Microsoft account, language settings sync across devices. To prevent any complications,...
by: Oralloy | last post by:
Hello folks, I am unable to find appropriate documentation on the type promotion of bit-fields when using the generalised comparison operator "<=>". The problem is that using the GNU compilers, it seems that the internal comparison operator "<=>" tries to promote arguments from unsigned to signed. This is as boiled down as I can make it. Here is my compilation command: g++-12 -std=c++20 -Wnarrowing bit_field.cpp Here is the code in...
by: tracyyun | last post by:
Dear forum friends, With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each protocol has its own unique characteristics and advantages, but as a user who is planning to build a smart home system, I am a bit confused by the choice of these technologies. I'm particularly interested in Zigbee because I've heard it does some...
by: isladogs | last post by:
The next Access Europe User Group meeting will be on Wednesday 1 May 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM). In this session, we are pleased to welcome a new presenter, Adolph Dupré who will be discussing some powerful techniques for using class modules. He will explain when you may want to use classes instead of User Defined Types (UDT). For example, to manage the data in unbound forms. Adolph will...
by: conductexam | last post by:
I have .net C# application in which I am extracting data from word file and save it in database particularly. To store word all data as it is I am converting the whole word file firstly in HTML and then checking html paragraph one by one. At the time of converting from word file to html my equations which are in the word document file was convert into image. Globals.ThisAddIn.Application.ActiveDocument.Select();...
by: TSSRALBI | last post by:
Hello I'm a network technician in training and I need your help. I am currently learning how to create and manage the different types of VPNs and I have a question about LAN-to-LAN VPNs. The last exercise I practiced was to create a LAN-to-LAN VPN between two Pfsense firewalls, by using IPSEC protocols. I succeeded, with both firewalls in the same network. But I'm wondering if it's possible to do the same thing, with 2 Pfsense firewalls...
by: 6302768590 | last post by:
Hai team i want code for transfer the data from one system to another through IP address by using C# our system has to for every 5mins then we have to update the data what the data is updated we have to send another system
by: muto222 | last post by:
How can i add a mobile payment intergratation into php mysql website.

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.