I am using a SQLDataReader to display the results of my stored procedure, however, I have been unable to have it display any records. I am not generating an error and if I write out reader.hasrows.tostring() it returns true so I know it is returning a single row as intended. I know I have data in all columns to display. Any guidance would be appreciated.
Dim sqlcon2 As SqlConnection = New SqlConnection(Session("ConnStrEP"))
sqlcon2.Open()
Dim sqlcomm2 As SqlCommand = New SqlCommand("up_GetGenInfo_E1_01_02", sqlcon2)
sqlcomm2.CommandType = Data.CommandType.StoredProcedure
sqlcomm2.Parameters.Add("AppNo", AppNo)
sqlcomm2.Parameters.Add("RevNo", RevNo)
Dim dt As SqlDataReader = sqlcomm2.ExecuteReader()
dt.Read()
Response.Write(dt.Item("PrName").ToString())
dt.Close()
sqlcomm2.Dispose()
sqlcon2.Close()
Do it in a following way:
Do While dt.Read()
Response.Write(dt.Item("PrName").ToString())
Loop
Related
Trying to update an old VB6 app to VB.Net. I am having trouble with syntax, I think. In any case it is a simple matter of inserting a new record to the autolog table. (code below).
I would like to ask something else that is often not documented too. It seems that I have to use command builders and so on - is there no way I can simply use an SQL statement and execute it against the background table? The tables are in Access while I am developing but will be scaled up on the final release of the software.
I have altered my code to the following by making use of the error suggestions at the foot of mygui.
It now looks like this and the only thing is that it is throwing a logic error at me which is that every end function must have a preceding "function". Perhaps I am being a little bit dim
Function MAutolog(ByVal Action As String) As Boolean
Dim SQL = "Insert Into Autolog (Action) Values (#Action)"
Using con As New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\PC User\Documents\Freightmaster\resources\freightmaster.accdb"),
cmd As New OleDb.OleDbCommand(SQL, con)
cmd.Parameters.Add("#Action", OleDb.OleDbType.VarChar).Value = Action
con.Open()
cmd.ExecuteNonQuery()
End Using
MAutolog = True
End Function
I would like to thank you for your help in advance. I can not tell you how much I will appreciate it.
Code
Module ModFunctions
Function MAutolog(ByVal UserID As Long, ByVal Action As String) As Boolean
Dim dbprovider As String
Dim dbsource As String
Dim mydocumentsfolder As String
Dim fulldatabasepath As String
Dim TheDatabase As String
Dim SQL As String
Dim DS As New DataSet
Dim da As OleDb.OleDbDataAdapter
Dim con As New OleDb.OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\PC User\Documents\Freightmaster\resources\freightmaster.accdb")
con.Open()
'----------------------------
SQL = "Select * from Autolog"
da = New OleDb.OleDbDataAdapter(SQL, con)
da.Fill(DS, "Log")
con.Close()
Dim CB As New OleDb.OleDbCommandBuilder(da)
Dim DSNEWROW As DataRow
DSNEWROW = DS.Tables("Log").NewRow()
DSNEWROW.Item("UserID") = UserID
DSNEWROW.Item("Action") = Action
DS.Tables("log").Rows.Add(DSNEWROW)
da.Update(DS, "log")
MAutolog = True
End function
Database objects like Connection and Command use unmanaged code and need their Dispose methods to release these resources. Either call this method on these objects or use Using...End Using blocks which will do this for you even if there is an error. In this code, both the Connection and Command are included in the Using block by separating them be a comma.
By Val is the default so is not necessary.
Always use parameters to avoid sql injection. Using values directly from user input can allow malicious code to be executed on your database. The value of a parameter is not considered as executable code by the database.
OleDb does not care about parameter names. You could just as easily use ? in the sql statement. I use names for readability. You do need some sort of name to add the parameter. OleDb considers the position of the parameter in the sql statement. The position must match the order that the parameters are added to the parameters collection.
This is the code for the Insert if UserID in an auto-number field. You do not provide a value for auto-number fields. The database will handle that.
Function MAutolog(Action As String) As Boolean
Dim SQL = "Insert Into Autolog (Action) Values (#Action)"
Using con As New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\PC User\Documents\Freightmaster\resources\freightmaster.accdb"),
cmd As New OleDbCommand(SQL, con)
cmd.Parameters.Add("#Action", OleDbType.VarChar).Value = Action
con.Open()
cmd.ExecuteNonQuery()
End Using
MAutolog = True
End Function
If UserID is not auto-number
Function MAutolog(UserID As Long, Action As String) As Boolean
Dim SQL = "Insert Into Autolog (UserID, Action) Values (#UserID, #Action)"
Using con As New OleDb.OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\PC User\Documents\Freightmaster\resources\freightmaster.accdb"),
cmd As New OleDbCommand(SQL, con)
cmd.Parameters.Add("#UserID", OleDbType.Integer).Value = UserID
cmd.Parameters.Add("#Action", OleDbType.VarChar).Value = Action
con.Open()
cmd.ExecuteNonQuery()
End Using
MAutolog = True
End Function
I have a SQL statement that, when ran in SSMS, returns 6 rows. After attaching the statement to the command text of a VB.NET SQLCommand with a command type of Text, reading it with a SqlDataReader, and attaching it to a dataset, the returned dataset only has 5 rows.
At first, I assumed it was an issue with the data. However, after several bouts of removing and adding rows to the source table with varying data, it was obvious that I was always getting the total row count - 1. I then decided to just use a SQLDataAdapter to populate the DataSet and the proper number of rows was returned.
Dim ds As New DataSet
Dim sqlCmd as New SqlCommand
Dim sqlCn As New SqlConnection
Dim sqlR As New SqlCommand
sqlCn.ConnectionString = "SomeConnectionString"
With sqlCmd.CommandText = "Select * from DummyTable"
.CommandType = CommandType.Text
.Connection = sqlCn
End With
sqlCn.Open()
sqlR = sqlCmd.ExecuteReader
sqlR.Read()
If sqlR.HasRows() Then
ds.Tables.Add("DummyTable")
ds.Tables(0).Load(sqlR)
return ds
End If
From here, I'm expecting to see the 6 rows from DummyTable. Instead, I'm seeing only 5.
However, if I use the following:
Dim da as SqlDataAdapter
Using sqlCn
da.SelectCommand = New SqlCommand(sqlCmd.CommandText, sqlCn)
da.Fill(ds)
End Using
Return ds
I get the full 6 rows. Is there something I'm missing about the way a DataSet's Tables.Add(tableName) or Tables(n).Load(dataReader) works? I had never worked with SqlDataReaders prior to this and was told to stick with them as our other projects use them.
Your code is already reading the first line of the query with the line sqlR.Read(). This line is unnecessary in your code. Remove it and it will work fine.
Also SqlCommand, SqlConnection and SqlDataReader implement iDisposable, so be sure to use using-statement with them:
Using sqlCn As New SqlConnection("SomeConnectionString")
sqlCn.Open()
Using sqlCmd as New SqlCommand
With sqlCmd.CommandText = "Select * from DummyTable"
.CommandType = CommandType.Text
.Connection = sqlCn
End With
Using sqlR As SqlDataReader = sqlCmd.ExecuteReader
If sqlR.HasRows() Then
Dim ds As New DataSet
ds.Tables.Add("DummyTable")
ds.Tables(0).Load(sqlR)
return ds
End If
End Using
End Using
End Using
I am trying to create a system that will load items from a database. There are two comboboxes; combobox1 which loads items from database table 1 and combox2 which loads items from database table 2.
Both tables are in the same database.
Here is was I tried but when I run the system I get this error:
(Conversion from string "SELECT * FROM dbo.Dishes" to type 'Long' is not valid.)
Here is the code I'm using:
Dim connection As New SqlConnection("Server = DESKTOP-1373H91; Initial Catalog = MealPreOrderSystem; Integrated Security = True")
connection.Open()
Dim query As String = "SELECT * FROM dbo.Dishes" And "SELECT * FROM dbo.Desserts"
Dim cmd As SqlCommand
cmd = New SqlCommand(query, connection)
Dim reader As SqlDataReader
reader = cmd.ExecuteReader
While reader.Read
cbxType.Items.Add(reader.Item("MealName"))
cbxType.Items.Add(reader.Item("DessertName"))
End While
connection.Close()
In VB.NET,AND is an operator.It is used to perform conjunction between either Booleans or Integers/Doubles/any numeric expression.Lets take your query string as an example :
Dim query As String = "SELECT * FROM dbo.Dishes" And "SELECT * FROM dbo.Desserts"
You are using AND here to join 2 sentences/strings which wouldn't result in anything rather it is trying to cast it as a Long.
Try to execute this command in SQL and you won't find any luck :(.
Your statements are correct :
SELECT * FROM dbo.Dishes
SELECT * FROM dbo.Desserts
But the way you are trying to achieve your goals is incorrect :(.
To get the data from the database into your combobox, what you can do is either use two comboboxes with separated SQL Queries/SQL Commands or you can use one combobox where you add data from both the databases but separate them with some special characters such as a comma ,
A sample may look like :
With one combobox
Dim cmd1 as new SqlCommand("SELECT * FROM dbo.Dishes",connection)
Dim dr as SqlDatareader = cmd1.ExecuteReader
While dr.Read
mycombo1.Items.Add(dr(0)) ' Here 0 is the column count,change it as required
End while
Dim cmd2 as new SqlCommand("SELECT * FROM dbo.Desserts",connection)
Dim dr2 as SqlDatareader = cmd2.ExecuteReader
While dr2.Read
mycombo2.Items.Add(dr2(0)) ' Here 0 is the column count,change it as required
End while
With 1 combobox
Here it gets a bit complicated.Firstly you need to populate your combobox from the data received from the first dataReader.Then, when the 2nd datareader is reading the data , you need to update the existing data/Item of the combobox keeping the existing data/item but adding new data/item to each existing data/item(separating them with ,).
Sample :
Dim i as Integer
Dim cmd1 as new SqlCommand("SELECT * FROM dbo.Dishes",connection)
Dim dr as SqlDatareader = cmd1.ExecuteReader
While dr.Read
mycombo1.Items.Add(dr(0))
End while
Dim cmd2 as new SqlCommand("SELECT * FROM dbo.Desserts",connection)
Dim dr2 as SqlDatareader = cmd2.ExecuteReader
While dr2.Read
mycombo1.Items(i) = myconbo1.Items(i) & "," & dr2(0)
i = i + 1
End while
Now, NOTE THAT I AM USING MULTIPLE DATAREADERS WITH THE SAME CONNECTION ,SO YOU MAY NEED TO INCLUDE MultipleActiveResultSets=True IN YOUR CONNECTION STRING or ENCLOSE THE DATAREADERS IN USING STATEMENTS or CALL dataReader.Close AFTER EACH DATAREADER HAS COMPLETED READING FROM THE DATABASE
This will solve your issue :)
Looks like you don't know how to write SQL queries (and your VB syntax itself looks faulty - string AND string?).
Dim connection As New SqlConnection("Server = DESKTOP-1373H91; Initial Catalog = MealPreOrderSystem; Integrated Security = True")
Dim query As String = <cmdString>
SELECT MealName as Name FROM dbo.Dishes
union
SELECT DessertName as Name FROM dbo.Desserts
</cmdString>
Dim cmd As SqlCommand
Dim reader As SqlDataReader
connection.Open()
cmd = New SqlCommand(query, connection)
reader = cmd.ExecuteReader
While reader.Read
cbxType.Items.Add(reader.Item("Name"))
End While
connection.Close()
Note: You are saying 2 comboboxes but your code seemed to be loading all the items to a single combobox. If you really need 2 comboboxes then use 2 SqlCommand and Reader loops (actually it would be better if you simply have used Linq for this).
You should be a bit more specific on what columns you are pulling from the 2 tables. if they are similar, you could write a sql query to UNION ALL the fields with a simple control to identify which record came from which table.
Example of SQL command string:
"SELECT 'M' AS Ctl, MealName AS aName FROM dbo.Dishes " &
"UNION ALL " &
"SELECT 'D' AS Ctl, DessertName AS aName FROM dbo.Desserts"
As mentioned by many here already, it seems like you are referencing only 1 ControlBox to list the fields returned cbxType
below is the reader (adapted to 2 ComboBoxes):
While reader.Read
Select Case reader.Item("Ctl")
Case "M"
cbxMType.Items.Add(reader.Item("aName"))
Case "D"
cbxDType.Items.Add(reader.Item("aName"))
End Select
End While
Hope this helps
So I have a MS Access Database with 1 table (Records) and 2 fields in it ("RecordID" (Number), which is the primary key, and "LowRes" (OLE Object) which is a low Resolution image). There are about 100 records.
I/m trying to load the Access Table into a DataTable (ID_Table) in VB.net.
Code so far:
Dim cnString As String = "Provider=Microsoft.ACE.OLEDB.12.0; Data Source=SBS2257_ID.accdb;"
Dim theQuery As String = "SELECT [RecordID], [LowRes] FROM [Records];"
Using CN As New OleDbConnection(cnString)
Dim command As New OleDbCommand(theQuery, CN)
Using objDataAdapter = New OleDbDataAdapter(command)
Dim ID_Table As New DataTable
CN.Open()
Dim pictureData As Byte() = DirectCast(command.ExecuteScalar(), Byte())
Dim picture As Image = Nothing
Using stream As New IO.MemoryStream(pictureData)
picture = Image.FromStream(stream)
objDataAdapter.Fill(ID_Table)
End Using
End Using
End Using
However the "DirectCast" command fails when I tell it to look at more then 1 field in my SQL statement with a datatype mismatch (if I just do [LowRes] it does not throw a error). However, I get stuck again when trying to apply the result to the table via the objDataAdapter, it doesnt fill the table with anything? I also notice that "picture" only contains the first image in the database.
I could put this database query in a function using "WHERE RECORDID=..." and loop it manually building the table returning "picture" each time, but Id like to avoid running a function 100 times, esp one that access a database.
Is it possible to read the whole database that contains images and just load it directly into a Datatable in one big swoop?
EDIT: So I got this to work:
Dim strConnection As String = "Provider=Microsoft.ACE.OLEDB.12.0; Data Source=SBS2257_ID.accdb;"
Dim strSQL As String = "SELECT [RecordID], [LowRes] FROM [Records];"
Using objConnection = New OleDbConnection(strConnection)
Using objCommand = New OleDbCommand(strSQL, objConnection)
Using objDataAdapter = New OleDbDataAdapter(objCommand)
Dim objDataTable As New DataTable("IDs")
objDataAdapter.Fill(objDataTable)
Return objDataTable
End Using
End Using
End Using
how ever when I go to view row 0, col 1 which should be the first LowRes image via a .ToString Useing this code:
Private Sub PrintValues(ByVal table As DataTable)
For Each row As DataRow In table.Rows
For Each col As DataColumn In table.Columns
MsgBox(row(col).ToString())
Next col
Next row
End Sub
It just displays "System.Byte[]". It knows its a Byte datatype, but how do I display that in a picturebox?
The ExecuteScalar() executes the query, and returns the first column of the first row in the result set returned by the query.
as your query is
Dim theQuery As String = "SELECT [RecordID], [LowRes] FROM [Records];"
the first column is RecordID which is not a Byte().
you can change your query as following:
Dim theQuery As String = "SELECT [LowRes] FROM [Records];"
or you have to use other methods to get data from the database
Dim strSql As String = "SELECT [RecordID], [LowRes] FROM [Records]"
Dim dtb As New DataTable
Using cnn As New OleDbConnection(connectionString)
cnn.Open()
Using dad As New OleDbDataAdapter(strSql, cnn)
dad.Fill(dtb)
End Using
cnn.Close()
End Using
Hey guys I need a little assistance in doing a basic search query from my form program to connect to an access database. basically I want to learn how to with the click of my query button, search text entered in a textbox and show the corresponding data in another text box, based on a match found. Any help would be greatly appreciated.
here is the code of my query button so far..
Private Sub btnQuery_Click(sender As Object, e As EventArgs) Handles btnQuery.Click
con = New System.Data.OleDb.OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\Eric\Documents\Fadv.accdb")
con.Open()
Dim id As Integer
Dim SQL As String = "SELECT FirstName, NAME FROM info WHERE FirstName=" & txtFirstName.Text & ""
Using cmd As New OleDbCommand(SQL, con)
id = Val(InputBox("Enter Query Criteria"))
MsgBox(SQL)
cmd.ExecuteNonQuery()
con.Close()
End Using
Im having a little trouble trying to figure out the (connectionstring) Im not sure if this is something I have to declare so far here is that my code, any guidance would be greatly appreciated.
` Private Sub btnQuery_Click(sender As Object, e As EventArgs) Handles btnQuery.Click
Using con As New OleDbCommand(connectionstring)
Dim cmd As New OleDbCommand(SQL, con)
con.open()
Dim reader As OleDbDataReader = cmd.ExecuteReader()
While reader.Read()
txtFirstName.Text = reader(0).ToString())
End While
reader.Close()
End Using
`
ExecuteNonQuery() is supposed to be used to write to the database, not read from it. "Although the ExecuteNonQuery returns no rows...[]" says the MSDN Documentation.
There's a couple ways to perform what you're trying to do. I suggest looking at the example here because it will show you how to perform a query using OleDb.
To get the data from your query to a textbox, you can do something like:
Using con As New OleDbConnection(connectionstring) //Your connection string
Dim command As New OleDbCommand(SQL, con)
connection.Open()
Dim reader As OleDbDataReader = command.ExecuteReader()
While reader.Read()
TextBox1.Text = reader(0).ToString())
End While
reader.Close()
End Using
This link provides even more clarification, and will greatly help you if you read what it has to say. Specifically:
"You use the Read method of the DataReader object to obtain a row from the results of the query. You can access each column of the returned row by passing the name or ordinal reference of the column to the DataReader. However, for best performance, the DataReader provides a series of methods that allow you to access column values in their native data types (GetDateTime, GetDouble, GetGuid, GetInt32, and so on)."
Also note: you want to paramaterize your queries.