[newbie] SQLCommand.ExecuteScalar does not convert to (string) - ASP.NET Discussion Boards

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Re: Datagrid

sudhanvag25-Jan-09 7:48

sudhanvag

25-Jan-09 7:48

Here[^] you can find some articles which will solve the problem.

Reporting

Brady Kelly22-Jan-09 5:44

Brady Kelly

22-Jan-09 5:44

Is it worth my while battling with the learning curve of the telerik reporting tool, or battling with trying to add grouping to GridViews? Any other recommendations?

All Sorted

Re: Reporting

ToddHileHoffer22-Jan-09 6:54

ToddHileHoffer

22-Jan-09 6:54

I would try the Telerik reporting tool. Because if you get stuck, you can post some questions on Telerik's site and they will help you out.

I didn't get any requirements for the signature

Re: Reporting

Brady Kelly22-Jan-09 7:12

Brady Kelly

22-Jan-09 7:12

Yeah, I think I'm going with it. I was looking at the Infragistics grid, but it's a bit heavyweight and twice the price. I just wonder how these people can make such awkward designers. People that complain about Microsoft's designers in Visual Studio don't seem to use many other designers.

All Sorted

Re: Reporting

VenkatFor.NET22-Jan-09 20:25

VenkatFor.NET

22-Jan-09 20:25

I believe using Telerik control will be a better idea as Telerik controls have more features. Based on the documentation and their examples, learning Telerik controls give you much better presentation as well.

Bhaskara

SQL Reporting Services

David Mujica25-Jan-09 2:04

David Mujica

25-Jan-09 2:04

If you are developing against MS-SQL server, why not consider SQL Server Reporting ? No extra charge if you alreay have MS-SQL server. My 2 cents. Smile | :)

Re: SQL Reporting Services

Brady Kelly25-Jan-09 2:53

Brady Kelly

25-Jan-09 2:53

I need to be able to switch the application between MySQL and MS SQL.

All Sorted

[newbie] SQLCommand.ExecuteScalar does not convert to (string)

jon-8022-Jan-09 4:45

jon-80

22-Jan-09 4:45

I'm trying to execute a simple command and pass it to a text box, however it does not seem to work.

Any idea why?

Confused | :confused:

//Insert to database and display task reference
            try
            {
                conAppDB.Open();
                // Retrieve latest taskID from database and display it.
                //:TODO  Update design, because of possible concurrent users.
                string getTaskRef = @"SELECT MAX([taskID_PK]) FROM [teamwiki].[dbo].[task];";  
                SqlCommand getTaskRefSQL = new SqlCommand(getTaskRef, conAppDB);
                if (getTaskRefSQL != null)
                {
                    txtTaskRef.Text = (string)getTaskRefSQL.ExecuteScalar(); 

// Note: Although the code passes through here, the value of getTaskRefSQL is null, is this a bug?

                }

            }
            catch (InvalidCastException)
            { 
                //Occurs when database is empty.
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally {
                conAppDB.Close();
            }

Environment
.NET framework 2.0.50727 SP1
Visual Studio 2005 Team Edition

Jon

Re: [newbie] SQLCommand.ExecuteScalar does not convert to (string)

Ashfield22-Jan-09 4:51

Ashfield

22-Jan-09 4:51

Have you tried running your sql directly? It may not be returning any data.

Bob
Ashfield Consultants Ltd
Proud to be a 2009 Code Project MVP

Re: [newbie] SQLCommand.ExecuteScalar does not convert to (string)

jon-8022-Jan-09 4:58

jon-80

22-Jan-09 4:58

Troubleshooting.

I tried using the following line and it returned the expected value on the screen, hence the SQL is working.

Response.Write(getTaskRefSQL.ExecuteScalar());

Jon

Re: [newbie] SQLCommand.ExecuteScalar does not convert to (string)

Colin Angus Mackay22-Jan-09 4:57

Colin Angus Mackay

22-Jan-09 4:57

The result of ExecuteScalar can be one of three things.

1. An object of the type you expect. String in this case
2. a DBNull which means that the value of the column you've selected is null
3. a null which means that the query returned no data. (please check for this rather than use an invalid cast exception)

Now, on to what you asked about:

jon_80 wrote:
Although the code passes through here, the value of getTaskRefSQL is null, is this a bug?

Are you sue that getTaskRefSQL is null. Unless you've missed something out of your code in the sample above there is no way getTaskRefSQL can be null at the point in the code you've said it is.

* Developer Day Scotland 2 - Free community conference
* The Blog of Colin Angus Mackay

Vogon Building and Loan advise that your planet is at risk if you do not keep up repayments on any mortgage secured upon it. Please remember that the force of gravity can go up as well as down.

Re: [newbie] SQLCommand.ExecuteScalar does not convert to (string)

jon-8022-Jan-09 5:11

jon-80

22-Jan-09 5:11

Colin Angus Mackay wrote:
jon_80 wrote:
Although the code passes through here, the value of getTaskRefSQL is null, is this a bug?

Are you sue that getTaskRefSQL is null. Unless you've missed something out of your code in the sample above there is no way getTaskRefSQL can be null at the point in the code you've said it is.

That's what I thought; I checked again and now it has a value, however before it was reading null in the watch window Smile | :)

Colin Angus Mackay wrote:
The result of ExecuteScalar can be one of three things.

1. An object of the type you expect. String in this case
2. a DBNull which means that the value of the column you've selected is null
3. a null which means that the query returned no data. (please check for this rather than use an invalid cast exception)

Explicit conversion was required because implicit conversion is not allowed by the compiler. I think can check for a DBNull using typeof presumably, however, since a value is being returned I'm not sure why the conversion is not working.

Related links:
http://msdn.microsoft.com/en-us/library/58918ffs(VS.71).aspx[^]

Jon

Re: [newbie] SQLCommand.ExecuteScalar does not convert to (string)

Colin Angus Mackay22-Jan-09 5:32

Colin Angus Mackay

22-Jan-09 5:32

jon_80 wrote:
Explicit conversion was required because implicit conversion is not allowed by the compiler.

I wasn't talking about that.

jon_80 wrote:
I think can check for a DBNull using typeof presumably

Try something like:

object rawValue = theSqlCommand.ExecuteScalar();
if (rawValue == DBNull.Value)
{
    //...
}
else
{
    string actualValue = (string)rawValue;
}

* Developer Day Scotland 2 - Free community conference
* The Blog of Colin Angus Mackay

Vogon Building and Loan advise that your planet is at risk if you do not keep up repayments on any mortgage secured upon it. Please remember that the force of gravity can go up as well as down.

Re: [newbie] SQLCommand.ExecuteScalar does not convert to (string)

jon-8022-Jan-09 20:50

jon-80

22-Jan-09 20:50

Thanks that worked.

Jon

Re: [newbie] SQLCommand.ExecuteScalar does not convert to (string)

Colin Angus Mackay22-Jan-09 5:08

Colin Angus Mackay

22-Jan-09 5:08

jon_80 wrote:
catch (Exception ex)
{
throw ex;
}

Also, don't do that. You lose valuable information in your exception if you do that. Detailed explanation about what happens when you re-throw an existing exception[^]

* Developer Day Scotland 2 - Free community conference
* The Blog of Colin Angus Mackay

Vogon Building and Loan advise that your planet is at risk if you do not keep up repayments on any mortgage secured upon it. Please remember that the force of gravity can go up as well as down.

Re: [newbie] SQLCommand.ExecuteScalar does not convert to (string)

jon-8022-Jan-09 7:12

jon-80

22-Jan-09 7:12

You're right I still haven't planned any error handling as yet Smile | :)

Jon

Delete Value from Cookie

Abdullah S. Abdelhay22-Jan-09 4:43

Abdullah S. Abdelhay

22-Jan-09 4:43

Hello All,
I want to delete value from cookie

For Example: The Cookie name [myCooke]
The Cookie Contains--------------------------------------------------------------------------------
myCookeLotID1=7amp;LotNo1=003462&LotName1=Lot 7&BuyPrice1=850&StockQuantity1=56
amp;amp;LotID2=5&LotNo2=003859&LotName2=Lot 3&BuyPrice2=154&StockQuantity2=2
localhost/1536149997862429993731246977484829981862*
---------------------------------------------------------------------------------------------------

The question: How i can delete [LotName2=Lot 3] value from this cookie?
please reply me quickly.

Thank you
Best Regards
Abdullah S. Abdelhay

Re: Delete Value from Cookie

Jon Rista22-Jan-09 6:32

Jon Rista

22-Jan-09 6:32

I am going to assume that the cookie contents arn't exactly as you typed it...because it seems there are a few typos in it. The following should work:

string cookie = "LotID1=7&LotNo1=003462&LotName1=Lot 7&BuyPrice1=850&StockQuantity1=56&LotID2=5&LotNo2=003859&LotName2=Lot 3&BuyPrice2=154&StockQuantity2=2";

string[] values = cookie.Split('&');

string[] newValues = (from cv in values
			let eqIdx = cv.IndexOf('=')
			let name = cv.Substring(0, eqIdx)
			let value = cv.Substring(eqIdx + 1)
			where name != "LotName2"
			select cv).ToArray();

string newCookie = String.Join("&", newValues);

Re: Delete Value from Cookie

rama charan22-Jan-09 17:47

rama charan

22-Jan-09 17:47

in Fact you cannot delete value from a cookie but
you should have to recreate the cookie with the new value as explained by the previous post.

Rama Charan Prasad

"Be happy and Keep smiling.Thats what u want be always.. Smile | :)

Re: Delete Value from Cookie

Rajdev Ramasamy26-Jan-09 22:28

Rajdev Ramasamy

26-Jan-09 22:28

We cannot delete a cookie actually. But one thing we can do is like, we can set the expiry date of the cookie to prior date, so that the browser will remove the cookie when it access the cookie for the next time, since it is expired.

Expiring the Cookie in Server Side:

if (Request.Cookies["MyCookie"] != null)
{
    HttpCookie myCookie = new HttpCookie("MyCookie");
    myCookie.Expires = DateTime.Now.AddDays(-1d);
    Response.Cookies.Add(myCookie);
}

<u>Expiring the Cookie in ClientSide Side:</u>

<script type="text/javascript">
<!--
  	deleteCookie('MyCookie');
// -->
</script>

Please reply on any doubts. Hope this will be usefull for you.

Thanks,
Rajdev KR

working with excel files version independantly in asp.net2.0

Nitin K22-Jan-09 3:47

Nitin K

22-Jan-09 3:47

hi all
This is my first question in the forum. i want to ask how to work with excel file independant of version problem in asp.net 2.0 like while reading excel file.?

Nitin

Re: working with excel files version independantly in asp.net2.0

Rutvik Dave22-Jan-09 3:56

Rutvik Dave

22-Jan-09 3:56

You need to install Excel on the web server on which you are developing asp.net application, so just install the latest version - 2007, and its backward compitable. so it can handle all the files of ,whatever version.

ASP.NET MVC

Brendan Vogt22-Jan-09 2:31

Brendan Vogt

22-Jan-09 2:31

Hi,

Can I please hear your views in using the MVP and MVC pattern? I want to use the web client software factory or ASP.NET MVC, but not sure which way to go. The website is a rather huge website. I was thinking to go woth the WCSF for now, and wait till ASP.NET MVC is in a more stable condition and then convert?

I have ready many articled on MVP and MVC, but still there is a confusion as to which one to use. WCSF makes use of DLLs which in my mind is faster, in the ASP.NET samples that I have see the code is just placed in folders, so because they are not already DLLs, wont it take longer to run?

Regards
Brendan

Re: ASP.NET MVC

ToddHileHoffer22-Jan-09 2:53

ToddHileHoffer

22-Jan-09 2:53

I have made many (over 50) asp.net applications both large and small. I have never seen the value in MVC or MVP.

I do separate the presentation and data layer and I implement themes. I use a master page and base page whenever possible and put all styling in the css file(s) in a theme. This makes it easy to change the presentation.

Adhering to a specific framework just seems to make more work without providing much benefit. The frameworks are good for developers who are less experienced with ASP.Net but if you know what you are doing than there is no need to constrict your development. Sometimes you just want to code a bit differently.

As for dlls, if you do not compile your website and just place code files IIS will compile the page the first time it is requested. The only advantage to compiling a web site is that the first user doesn't have to wait for it to compile.

I didn't get any requirements for the signature

Re: ASP.NET MVC

Not Active22-Jan-09 3:24

Not Active

22-Jan-09 3:24

ASP.NET MVC is stable, a release candidate is available http://weblogs.asp.net/scottgu/archive/2008/12/19/asp-net-mvc-design-gallery-and-upcoming-view-improvements-with-the-asp-net-mvc-release-candidate.aspx[^]

ASP.NET MVC is a tool just like any other, it will have benefits in some situations and not in others. It's up to you to understand the pros and cons and choose the correct tool for the job.

only two letters away from being an asset

Last Visit: 31-Dec-99 18:00 Last Update: 30-Apr-24 23:31

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