I am new to asp.net and here I am trying to populate a single text box with a value from database.
I have created this code but not working:
Try
Dim MyCon As New SqlConnection("server = servername; uid = sa; pwd =abc; database = master")
Dim MyCommand As New SqlCommand("Select empFirstName from Employees where empid=2")
MyCon.Open()
Dim MyReader = MyCommand.ExecuteReader()
While MyReader.Read()
Dim sqlda = New SqlDataAdapter()
Dim dt As New Data.DataTable()
Dim ds As New Data.DataSet
sqlda.Fill(ds)
TextBox1.Text = ds.Tables(0).ToString
MyCon.Close()
End While
Please correct the code and tell me where I am wrong.
Kindly suggest me a link if any to read more on this topic for beginners with example.
Try this sample, it will work for you http://geekswithblogs.net/dotNETvinz/archive/2008/09/12/bind-textbox-and-label-control-with-data-from-database.aspx
ds.Tables(0)
will return a DataTable
If you want to get the tablename, write this instead:
ds.Tables(0).TableName
If you want to get value returned, write this kind of code:
ds.Tables(0).Rows(0).Item("empFirstName")
This will store only the 1st row from the database
TextBox1.Text = ds.Tables(0).Rows(0)(0).ToString();
Row(0)(0) indicates to get the 1st row from the 1st column
If the query is returning more than 1 rows then u need to iterate the data table and store it in a List(Of String) instead of an array as you don't know the number of rows returned from the query
Dim EmpFirstName As New List(Of String)
Dim myRow As DataRow
Dim myColumn As DataColumn
For Each myRow in dt.Rows
EmpFirstName.Add(myRow(dt.Columns(0)))
Next
Related
I need pass the whole table to a stored procedure to run a update query.
This is my code:
CREATE TYPE [dbo].[UploadData] AS TABLE
(
[CODE] [varchar](4) NULL,
[SERIALNUMBER] [varchar](20) NULL,
[PRODUCTCODE] [varchar](20) NULL,
[THRESHOLD] [int] NULL
)
This is my stored procedure:
CREATE PROCEDURE sp_UpdateExchangeThreshold
#TableType dbo.UploadData READONLY
UPDATE [dbo].[ExchangeData_20221213]
SET t.Threshold = tbl.THRESHOLD
FROM [dbo].[ExchangeData_20221213] t
INNER JOIN #TableType AS tbl ON t.ProductCode = tbl.PRODUCTCODE
AND t.SerialNumber = tbl.SERIALNUMBER
In my VB.Net code, I have this:
Using sqlCommand As SqlCommand = New SqlCommand()
sqlCommand.Connection = connection
sqlCommand.CommandText = "sp_UpdateExchangeThreshold"
sqlCommand.CommandTimeout = 180
sqlCommand.CommandType = CommandType.StoredProcedure
Dim parameterList As SqlParameter = New SqlParameter("#TableType", SqlDbType.Structured)
parameterList.Value = dataTable
parameterList.Direction = ParameterDirection.Input
sqlCommand.Parameters.Add(parameterList)
sqlCommand.ExecuteNonQuery()
End Using
I'm not able to update the records. Any mistake I made? Please help
Unfortunately, a .NET ADO datatable is NOT a SQL Server table type. They have NOHTING to do with each other. You can use a datatable with Oracle, MySQL, or any server based system. You can even use a access database with a data table.
So, datatable object is platform gnostic (neutral), and thus can't be passed, used as a SQL table type.
However, you don't really have to pass a table back. The REAL question is what do you want to do with this table?
Do you want to edit, or update or insert rows from that table back into the database?
If yes, then use a table adaptor (that's what they are for).
Not only will they do all the dirty work for you, but that table can have updates, deletes, edits and insert/additions.
And with ONE command you can send that WHOLE table + all edit/update/delete/adds in one shot.
Say like this:
Dim rstHotels As New DataTable
Using conn As New SqlConnection(My.Settings.TEST4)
Dim strSQL As String = "SELECT * FROM tblHotelsD"
Using cmdSQL As New SqlCommand(strSQL, conn)
conn.Open()
rstData.Load(cmdSQL.ExecuteReader)
' delete first row
rstData.Rows(0).Delete() ' delete first row
rstData.Rows(2).Item("City") = "Zoo" ' edit/modify the 3rd row
Dim OneNewRow As DataRow = rstData.NewRow
OneNewRow("FirstName") = "First Name"
OneNewRow("LastName") = "last Name"
OneNewRow("HotelName") = "My Hotel Name"
OneNewRow("Active") = True
rstData.Rows.Add(OneNewRow)
' now, lets send edits/delete/inserts back to database.
Dim da As New SqlDataAdapter(cmdSQL)
Dim daU As New SqlCommandBuilder(da)
da.Update(rstData)
End Using
End Using
Now, I have the load the table and the update as per above, but they can be done separately.
Edit: Sending the datatable to SQL Server, but not all rows.
' so, lets "send" to the sql database some data
Dim rstData2 As New DataTable
rstData2.Columns.Add("HotelName", GetType(String))
rstData2.Columns.Add("City") ' FYI -- defualt is string
rstData2.Columns.Add("Active", GetType(Boolean))
' lets create 5 test rows of data
For i = 1 To 5
Dim MyNewRow As DataRow = rstData2.NewRow
MyNewRow("HotelName") = "Hotel #" & i
MyNewRow("City") = "City #" & i
MyNewRow("Active") = True ' you MUST include columnes that require deffault value
rstData2.Rows.Add(MyNewRow)
Next
' now send in one shot to database
Using conn As New SqlConnection(My.Settings.TEST4)
Dim strSQL As String = "SELECT ID, HotelName, City, Active FROM tblHotelsD"
Using cmdSQL As New SqlCommand(strSQL, conn)
conn.Open()
Dim da As New SqlDataAdapter(cmdSQL)
Dim daU As New SqlCommandBuilder(da)
da.Update(rstData2)
End Using
End Using
How do you rebind the data in Gridview to show 50 and up instead of 1 and up.
Starts from 1:
Dim connStr, cmdStr As String
Dim myDataSet As New DataSet
Dim dt As New DataTable()
connStr = "connection string works"
cmdStr = "SELECT * FROM table1;"
Try
Using conn As New SqlConnection(connStr)
Using cmd As New SqlCommand(cmdStr, conn)
conn.Open()
cmd.ExecuteNonQuery()
Using myDataAdapter As New SqlDataAdapter(cmd)
myDataAdapter.Fill(myDataSet)
dt = myDataSet.Tables(0)
GridView1.DataSource = dt
GridView1.DataBind()
End Using
conn.Close()
cmd.Dispose()
conn.Dispose()
End Using
End Using
Catch ex As Exception
End Try
What do I need to change to start from 50 and up?
Make your DataTable an enumerable object and then use LINQ's .Skip() function to get past the first 50 items, like this:
Dim filteredSet = dt.AsEnumerable().Skip(50)
Now bind the filteredSet instead of dt to the grid view, like this:
GridView1.DataSource = filteredSet
GridView1.DataBind()
I would say the most efficient choice would be to not select the data from the database by using a parametrized query where you pass in a starting value of some sort and the query only selects data occurring after this point.
Another option, which only takes a small adjustment to your code is to simply delete rows from the DataTable like so:
' remove the first 50 rows
For x As Integer = 1 To 50
dt.Rows.RemoveAt(0)
Next
I'm having a problem populating a child gridview using a function I define. I keep getting the error "Object reference not set to an instance of an object". What am I doing wrong? Am I using the FindControl function incorrectly? It doesn't seem to find the child gridview.
Sub RecordsByZip()
Dim DBConn As New SqlConnection(Application("DBConn"))
Dim gv1 As GridView
gv1 = grdTotal
Dim gv2 As GridView
gv2 = DirectCast(gv1.FindControl("grdChild"), GridView)
Dim ZipCode = lbZip.SelectedItem
For Each ZipCode In lbZip.Items
If ZipCode.Selected = True Then
Dim cmdZip As SqlCommand = New SqlCommand("spPICAInsertTotals2", DBConn)
cmdZip.CommandType = CommandType.StoredProcedure
strZip = ZipCode.Text
strUser = Session("User")
Dim Zip As New SqlParameter("#Zip", SqlDbType.VarChar)
Zip.Value = strZip
cmdZip.Parameters.Add(Zip)
Dim UserID As New SqlParameter("#UserID", SqlDbType.Int)
UserID.Value = strUser
cmdZip.Parameters.Add(UserID)
DBConn.Open()
gv1.DataSource = cmdZip.ExecuteReader
gv1.DataBind()
gv1.Visible = True
DBConn.Close()
End If
Next
btnExport.Visible = True
lblmsg.Visible = False
' Dim DBConn = New SqlConnection(Application("DBConn"))
Dim cmdCounty As SqlCommand = New SqlCommand("spPICAInsertTotals", DBConn)
cmdCounty.CommandType = CommandType.StoredProcedure
'Dim gv As GridView = TryCast(e.Row.FindControl("grdChild"), GridView)
strUser = Session("User")
Dim UserID2 As New SqlParameter("#UserID", SqlDbType.Int)
UserID2.Value = strUser
cmdCounty.Parameters.Add(UserID2)
DBConn.Open()
gv2.DataSource = cmdCounty.ExecuteReader
gv2.DataBind()
gv2.Visible = True
DBConn.Close()
btnExport.Visible = True
lblmsg.Visible = False
lblInstructions.Visible = False
End Sub
First of all . . .
Just as a disclaimer, I normally use repeater controls instead of gridview controls.
But this may help you . . .
I can tell you that with repeater controls, if you want to find a nested repeater then you must look for them inside the item of the parent repeater to which they belong. Essentially, what you are trying to do with the code above, is find grdChild when there might actually be several grdChild (it is a nested gridview, after all). I'd be willing to bet this is where you're object reference error is occurring.
In other words, if you want to find the nested repeater with the ID nestedRepeater, and you know it is located in the first item of your main repeater (which in this case I've assigned to the myRepeater variable), you can do this:
Dim myItem as RepeaterItem = myRepeater.Items(0)
Dim Rep2 as Repeater = myItem.FindControl("nestedRepeater")
Using SqlDataAdapter and a DataSet (recommended)
Dim sa As New SqlDataAdapter(cmdCounty) 'Initialize the SqlDataAdapter and assign the SqlCommand object to it.
Dim ds As New DataSet() 'Initialize the DataSet (we will bind this to the gridview)
Try 'The Try/Catch statements help you to handle errors.
cmdCounty.Connection.Open() 'Open the connection to the database.
sa.Fill(ds) 'This statement uses the SqlDataAdapter to easily execute the SqlCommand (using the query specified in the SqlCommand object) and . . .
'. . .use that data to fill our dataset.
cmdCounty.Connection.Close() 'These statement close the connection and dispose of the SqlCommand object. Note: You may only need the dispose command.
cmdCounty.Dispose()
Catch ex As Exception
'Catch your error here.
cmdCounty.Connection.Close()
cmdCounty.Dispose()
End Try
gv2.DataSource = ds 'Set the datasource for your GridView control.
gv2.DataBind() 'Bind the data.
Using SqlDataReader and a DataTable
According to your comment, you're code is breaking when you assign the gridview to the cmd.ExecuteReader.
You will need to access your data using a method like this:
Dim rdr as SqlDataReader = cmdCounty.ExecuteReader() 'Declare the SqlDataReader and set it to handle your SqlCommand.
Dim dt as New DataTable 'Initialize a new DataTable. This is where we will place the information we read using the SqlDataReader.
'Make sure you add the columns...
dt.Columns.Add("firstColumnName") 'Create a column for each field you will be retrieving data from.
dt.Columns.Add("secondColumnName")
Dim r as DataRow 'Declare the variable r as a DataRow.
'You may want to insert the line "If rdr.HasRows Then" to check if any data was pulled before attempting to read it.
While rdr.Read() 'Loop through each row in the reader.
r = dt.NewRow() 'Set r to equal a new DataTable in the DataTable we created. Note: This does not actually add the row to the table.
r("firstColumnName") = rdr("firstColumnName") 'Set the values of each column in the current DataRow to equal their corresponding data read from SQL.
r("secondColumnName") = rdr("secondColumnName")
dt.Rows.Add(r) 'Add the DataRow r to the DataTable.
End While 'Loop back until there are no more rows.
gv2.DataSource = dt
gv2.DataBind()
Both of these examples assume you have already created your SqlCommand object and have assigned a working SQL query string and Connection object to it.
I've seen a couple example of how to do this by placing all the code in the aspx file, but I'm trying to do it from the code-behind. Here's what I have in the code behind:
Dim dt As New DataTable
Using conn As New OleDbConnection(ConnectionString)
conn.Open()
Dim dtAdapter As New OleDbDataAdapter
Dim command As New OleDbCommand("SELECT * FROM table " & _
"" _
, conn)
dtAdapter.SelectCommand = command
dtAdapter.Fill(dt)
conn.Close()
End Using
GridView1.DataSource = dt
GridView1.DataBind()
I'm open to any solutions, but I would prefer to do it in the code-behind if possible since thats how the rest of app is. I dont need to necessarily use a gridview just display some tabular data, so whatever works is fine. Im trying to avoid manually constructing sql strings. Any thoughts?
I don't see the question. If you don't kno how to filter the records in your query, use the Where clause with a parameter:
Dim dt = New DataTable()
Using conn As New OleDbConnection(ConnectionString)
Dim queryString As String = "SELECT * FROM Table WHERE Field1 LIKE ?"
Dim command As OleDbCommand = New OleDbCommand(queryString, conn)
command.Parameters.Add("#p1", OleDbType.Char, 3).Value = "a%"
Using da = New OleDbDataAdapter(command)
' you don't need to open/close a connection if you use DataAdapter.Fill
da.Fill(dt)
End Using
End Using
GridView1.DataSource = dt
GridView1.DataBind()
DataAdapter Parameters
Using Statement
I have a couple of problems relating to one of the parameters passing a number of values to a stored procedure and the result that comes back converting to dataset in order for this to be bound to an MS ReportViewer.
The error I am getting says that the the reader is closed.
My relevant code snippet is:
Dim _listOfSites As New StringBuilder()
Dim _resultDataSet As DataSet = New DataSet
Using _conn as New SqlConnection()
_conn.ConnectionString = _connString
Try
For i as Integer = 0 To _sites.Count - 1
_listOfSites.Append(_sites(i))
If _sites.Count > 1 Then
_listOfSites.Append(",")
End If
Next
_conn.Open()
Dim _sqlCommand as SqlCommand = New SqlCommand("GetResults", _conn)
_sqlCommand.Parameters.Add("#Sites", SqlDbType.Varchar).Value = _listOfSites
_sqlCommand.Parameters.Add("#Date", SqlDbType.Date).Value = _date
Dim _reader as SqlDataReader = _sqlCommand.ExecuteReader
While _reader.Read
_resultDataSet.Load(_reader, LoadOption.PreserveChanges, New String() {"RegionalResults"})
End While
_reader.Close()
Can anyone please help?
Thanks
Looks like you should not call _reader.Read as _resultDataSet.Load do it by itself and it could close the SqlDataReader. So instead of
Dim _reader as SqlDataReader = _sqlCommand.ExecuteReader
While _reader.Read
_resultDataSet.Load(_reader, LoadOption.PreserveChanges, New String() {"RegionalResults"})
End While
_reader.Close()
Just write
Using _reader as SqlDataReader = _sqlCommand.ExecuteReader
_resultDataSet.Load(_reader, LoadOption.PreserveChanges, New String() {"RegionalResults"})
End Using
Hope that helps