DataSource Controls :: NULL Value Returned From Database And Handling It
Feb 14, 2010
I'm developing a website using asp.net 2.0 . I have retrieved a record from database through the query.
SqlConnection con = new SqlConnection(connectionstring);
con.Open();
String SQL = "SELECT * FROM Table where attribute1 = value";
SqlCommand cmd = new SqlCommand(SQL, con);
SqlDataReader reader = cmd.ExecuteReader();
Sometimes, there is no record matching this query and so null value is retrieved. My question is how to find that the null value is returned. Since If (no record found i.e NULL) certain actions needs to be done and if (records found i.e NOT NULL) ceratin different actions needs to be carried out.
I now want to count the number of returned rows so that I can say:IF rows_returned = 1 then login else deny I think you get the idea.P.S. I know this is not the most secure method of login but I do not want to use the ASP.NET configuration manager as I like to understand what is happening. I am starting off very simple and I shall work up from there.
I have a datareader like so but when it encounters a NULL database value, I get the error message "Conversion from type 'DBNull' to type 'String' is not valid."
Dim myReader As SqlDataReader = myCommand.ExecuteReader() Dim yValues As New List(Of Double) With myReader If .HasRows Then While .Read yValues.Add(Double.Parse(.GetValue(0)))........
here is my code which is working fine to read batabase image from database but if there is NULL value in database so how can i read physical path noimage.jpg
I have a rather large formview that asks for a variety of input values (physical totals vs pos report totals). I have created vb code to calculate the differences and subtotals of various types prior to inserting the data so people can check for entry errors.
Its a closing reconciliation form. Here's the problem: If they forget to enter 0 in a field that doesn't have any totals, a big ugly error message displays. I would like to avoid this. I can tell them until I am blue in the face to remember to enter 0 and not leave any blank fields, but realistically its going to happen and I need to handle it in the programming.
I have been struggling to either default the values to zero to start with, replace a null textbox with 0 before the calculate runs...but I can't get anything to really work. What is the best way to handle this?
Here is the aspx page:
[Code]....
And the code behind page with working "Calculate" as long as fields are not left blank (I took out all the test code that made it not work at all)
[Code]....
Finally, the error message I am getting is the following:
[Code]....
I can't seem to find the right combination of programming to account for the "" string to be 0 so that it will add or subtract values in my calculate. I have my sql table setup with default values of 0 so if a field is left blank it will be entered into the database as 0 and not null. It is really just for my inserting of a reconciliation and the running of Calculate Totals to double check their work prior to inserting into the database.
I have a website which displays news information. It displays the titles at the default (home) page and when click it shows the full story.
I use object datasource to load the news titles.
Now, sometimes the database server lose its connection or changes to the database and it affects the whole website because error is reported at the Application level. I would like the Home page to still show but the section where the news titles usually appears will now show an error message that the database is down (Refer below my part of my code).
How can I achieve that?? I tried to do that at the page_error level but it displays nothing. I don't want to pass the error to application level, I want to handle at datasource load/binding level so that it display this error message at the news section and other home website information can still be shown.
I have setup my business object to have a create_date and edit_date members both datetime datatypes. My company want to display the create_date and edit_date fields in a gridview for each transaction. The problem i have is that after insterting a record it will have a valid create_date but no edit_date and when displayed in the gridview it defaults to datetime.minvalue (My default). How on earth do i show an empty field in my gridview for a null datetime field in the database?
I am using similar architecture to the Imar Spaanjaars example of a tiered solution. With a few small tweeks it has worked well for me for ages. I am passing a List<Database> to my object datasource which connects to my gridview.
im working on visual Studio 2010, and i have an error on an update.
this is the code in VB.
[Code]....
Thats the code and the error is:
Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.`
When a sql query returns NULL , I can use the following code to evaluate:
[Code]....
When a sql query returns nothing, neither IsDBNull nor is Nothing works. I don't know why some sql queries return null while some return nothing when there are no data returned. But anyway, can somebody tell me how to evaluate nothing value returned in sql datareader in vb.net? When I put the cursor over signInfo variable in debug mode, I can see Nothing show as its value. But the line does not work
I've managed to connect to the database and return a record based upon a login name. I can itterate through the rows printing out the password but I know there's only 1 row (or can test for that) so how do I get the value of the password for the one row without the loop?
Dim supervisorAdapter As New SupervisorTableAdapters.SupervisorTableAdapter Dim supervisors As Supervisor.SupervisorDataTable supervisors = supervisorAdapter.GetSupervisorByLogin(login) For Each count As Supervisor.SupervisorRow In supervisors Response.Write(count.password) Next
I want this query to return all distinct properties and a thumbnail image. However some properties don't have thumbnail images and they don't get returned by the query. If the imgid is null I still want to return the property. Not sure of how to do this.
i have a webpage built in asp.net c#. it always a user to create a new record in a db table. there are there are two input fields, text and score. text cannot be a null value so if the user doesn't input text onsubmit, the page errors out. i want to throw in some simple error handling code in the code behind page. i've tried including an if/else on_inserted method but ran into some java script errors.
I am viewing items returned from a dataset in an Infragistics chart control. My problem is that due to a weak point in the control, I am left looking for a way to manipulate the height of the chart based on the count/number of items returned by the ObjectDataSource(DataSet).
Does anyone one have an existing C# sample they could let me view of accessing the count of records returned within the code-behind of a page that I could then use within a case statement to set the hight of the control?
I want to run a SUM on a particular against the DataSet returned by a SqlDataSource. How can I access the DataSet stored in memory that is returned by the SqlDataSource to run this calculation?
I am having some difficulties with a particular task. I am creating a support desk intranet application and I am trying to write a method within a class within a namespace which will form a generic database connection which can be called from any of the aspx pages so that I have the dbconnection logic in one place; you know, going along with the 'DRY' (Don't Repeat Yourself) mantra.
The Namespace:
SUPPORTDESK.SQL.dbconnection.pullData()
Objective of the method:
To provide any aspx code behind file with an SQL Server 2005 Express Connection and if possible return the data from an SQL Query. This is where I need advice do I create the method such that it simply forms the connection and returns a DataSet or that it returns an SQLConnection object? If i've got things back to front and upside down don't worry I'm a beginner with ASP.NET. The Method so far:
[Code]....
If I'm on the right track how do I access the data returned in the DataSet?
I have a stored procedure 'RoomIfExists' on my sql server (it does work). It takes a string variable for the Room_No and returns either '1' or '2' depending on the result of the query.
[Code]....
I need to know how to run the sp in c#, passing the variable Room_No and then pull the result from it.I am using a data reader.
I'm attempting to further reduce a dataset/table by various user input. Part of this process is grouping the data by a timestamp prior to a summation. I'm trying to use LINQ and cannot get the data returned that I need.
string strConString = ConfigurationSettings.AppSettings[ "conString" ]; myConnection = new OdbcConnection(strConString); myConnection.Open(); // open connection string strSelect= "select * from tbl_howells_product_data where title like" + "'" + strsearch + "%" +"'" + "order by product_id asc"; OdbcCommand myCommand = new OdbcCommand(strSelect, myConnection); dtrReader=myCommand.ExecuteReader();
The problem is I need to check to see if any data has been returned from the SQL query, if there are no rows/ data returned by the query then I need to display a message to say that there aren't. I know that there isn't a 'number of rows method' for the dtrReader, so does anybody know how I could do this?
This may not be the correct place to put this as it is both a stored procedure AND Visual Studio 2008 problem.
I have the following stored procedure:
[Code]....
I have been mokeying around with it because of what is happening. I have a dataset, call it dataset1. I drag this stored procedure onto the dataset. I EXPECT a datatable to appear, instead the data set adds this store procedure to the queries table adapter and sets the exec mode to 'NonQuery' which unless I am very mistaken, means "don't expect a dataset back from this' when in fact you DO expect a dataset back from this.
The SQL server is a Windows 2000 Server running SQL 2000. It has never caused us a moments grief since we set it up oh-so-many years ago.
If I connect to a different database and drag a query into the same dataset I get a datatable as I expect. I cannot see where / how this procedure could be wrong. The query when executed returns exactly the data I expect, in the format I expect (looks like a table, acts like a table in the Query analyzer).
