I cannot seem to find the answer to my problem anywhere on the internet. I have seen solutions for others such as adding keys to appsettings etc, none of which have worked for me.
Imports Oracle.DataAccess.Client
Imports Oracle.DataAccess.Types
Imports System.Data
Sub Button1Click(sender As Object, e As EventArgs)
Dim oradb As String = "DATA SOURCE=INITIATE;PASSWORD=pASS;PERSIST SECURITY INFO=True;USER ID=uSER"
Dim conn As New OracleConnection(oradb)
Try
Dim sql As String = "select MEMRECNO from INIT.MPI_MEMHEAD where MEMIDNUM = '" + txtMRN.Text + "'"
Dim cmd As New OracleCommand(sql, conn)
cmd.CommandType = CommandType.Text
Dim dr As OracleDataReader = cmd.ExecuteReader()
dr.Read()
txt1.Text = dr.GetInt32(0)
Catch ex As Exception
richTextBox1.Text = richTextBox1.Text + vbCrLf + ex.Message
End Try
End Sub
Now, when I run this code, if I enter a value in the top 25 records (when visually looking at the table in Oracle) it returns the result. However, when I enter a value that might be record number 1 million, i get this error: "Operation is not valid due to the current state of the object."
Yes, the value does exist. Because if I run the exact same query in Oracle, I get the result.
This leads me to believe that the connection is timing out, closing, or there is a limit on how many rows can be returned using the Oracle Data Access Client.
Related
Can you please help me, what the problem of my code:
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
'UPDATE Data
openCon()
Try
cmd.Connection = con
cmd.CommandText = "UPDATE emp_table SET FNAME = '" & TextBox1.Text & "', LNAME= '" & TextBox2.Text & "', AGE = '" & TextBox3.Text & "', GENDER ='" & Gender & "', OFFICE STAFF= '" & ComboBox1.Text & "' Where ID ='" & TxtID.Text & "' "
cmd.ExecuteNonQuery()
con.Close()
MsgBox("Suceessfully Updated Record")
TxtID.Clear()
TextBox1.Clear()
TextBox2.Clear()
TextBox3.Clear()
RBMale.Checked = False
RBFemale.Checked = False
ComboBox1.Text = ""
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End Sub
There are many problems in your code and if you look around this site I think you will find many partial answers that step by step will help you solve your problems. So I try to give you an answer where all the problems are examined, discussed and solved.
First problem: How do you handle the connection.
It seems that you have a global connection instance called con that you open with openCon. This is not a good approach and always a source of problems. You always need to check if the connection is closed properly or not. For example, in the code above you have forgot to close the connection in case of exception and this will lead to other exceptions in some code not related to this one. You keep resources on the server locked to you and this will decrease the performance of every one connection to that server.
I would change your openCon to this
Public Function openCon() as MySqlConnection
Dim con as MySqlConnection = new MySqlConnection(....here connection string ...)
con.Open()
return con
End Function
This will create a new instance of the MySqlConnection every time you call this method Now you can remove the global connection instance and use the one returned by openCon in this way
Using con As MySqlConnection = openCon()
.... code that use the local con object
End Using
This will close and destroy the connection even if an exception occurs inside the Using block and the ADO.NET libraries are smart enough to use a thing called Connection Pooling to reduce the time required to build and open a connection with the same connection string.
Second problem: The syntax error.
Looking at the point of the error suggested by the message I can see a field name composed by two words separated by a space. This is fine, but then you should remember that the sql parser cannot understand this and you need to help it enclosing the two words in a backtick character (ALT+096) so the parser understand that this is a single field name. Given the fact column names are an internal information of no concern for your end user then why use spaces in column names? If possible remove the space in column names.
Third problem: Sql Injection and other syntax errors
You are concatenating strings to build an sql command. But this is an easy target for wannabe hackers. Suppose that I write in your textBox1 this string instead of a First Name: Mario'; --
Then your command becomes
UPDATE emp_table SET FNAME = 'Mario'; -- xxxxxxxxxxxx
everything after -- is considered a comment and the query is still executable, but it changes every record in emp_table to have a first name equal to Mario.
But the query could fail as well if someone writes a Last Name that contains an apostrophe like O'Leary just now the query is no more syntactically valid.
The solution to this is always one. Use Parameters.
Recap of changes to your code.
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
Dim cmdText as String = "UPDATE emp_table SET FNAME = #fname,
LNAME= #lname, AGE = #age, GENDER =#gender,
`OFFICE STAFF` = #staff
Where ID =#id"
Using con as MySqlConnection = openCon()
Using cmd as MySqlCommand = new MySqlCommand(cmdText, con)
Try
cmd.Parameters.Add("#fname", MySqlDbType.VarChar).Value = textBox1.Text
cmd.Parameters.Add("#lname", MySqlDbType.VarChar).Value = textBox2.Text
cmd.Parameters.Add("#age", MySqlDbType.VarChar).Value = textBox3.Text
cmd.Parameters.Add("#gender", MySqlDbType.VarChar).Value = gender
cmd.Parameters.Add("#staff", MySqlDbType.VarChar).Value = combobox1.Text
cmd.Parameters.Add("#id", MySqlDbType.VarChar).Value = txtID.Text
cmd.ExecuteNonQuery()
MsgBox("Suceessfully Updated Record")
TxtID.Clear()
TextBox1.Clear()
TextBox2.Clear()
TextBox3.Clear()
RBMale.Checked = False
RBFemale.Checked = False
ComboBox1.Text = ""
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End Using
End Using
End Sub
In the recap I have added parameters for every single field that you want to update. But remember. Parameters should have a Type (The MySqlDbType here) that should match the type of the field and the value should be of the same type. For example it seems improbable that Age is a varchar field. So you should convert TextBox3.Text to an integer if the field is an integer.
I want to be able to read a value (in this case an Group ID). All the topics and tutorials I've watched/read take the data and put it into a textbox.
I don't want to put it in a textbox in this case; I want to grab the Group ID and then say:
If Group ID = 4 then login
Here is an image of the database.
Basically, but none of the tutorials I watch or the multiple forums. None of them take a a value and say if value = 4 then login or do something else.
If text = "1" Then
MysqlConn = New MySqlConnection
MysqlConn.ConnectionString =
"server='ip of server'.; username=; password=; database="
Dim READER As MySqlDataReader
Dim member_group_id As String
Try
MysqlConn.Open()
Dim Query As String
Query = "SELECT * FROM `core_members` where name='" & TextBox2.Text & "'"
Query = "SELECT * FROM `nexus_licensekeys` where lkey_key='" & TextBox1.Text & "'"
COMMAND = New MySqlCommand(Query, MysqlConn)
READER = COMMAND.ExecuteReader
Dim count As Integer
count = 0
While READER.Read
count = count + 1
End While
Here is what I have so far. I'm kind of new implementing mysql data with visual basic and only recently started to get into it. I'm not sure what comes next or how to even start with reading the group id etc.
As I said any help from here on out would be highly appreciated of how to read the group id and say if this group id = this number then do this or that. I'm sure you get the idea.
I divided the code into UI Sub, and Data Access Function that can return data to the UI. Your Event procedure code should be rather brief and the functions should have a single purpose.
Keep your database objects local to the method. This way you can have better control. The Using...End Using blocks ensure that your database objects are closed and disposed even if there is an error.
I leave it to you to add validation code. Checking for empty TextBox or no return of records.
I hope this serves as a quick introduction to using ADO.net. The take away is:
Use Parameters
Make sure connections are closed. (Using blocks)
Private ConnString As String = "server=ip of server; username=; password=; database="
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim GroupID As String = GetGroupID(TextBox1.Text)
If GroupID = "4" Then
'your code here
End If
Dim LocalTable As DataTable = GetLicenseKeysData(TextBox1.Text)
'Get the count
Dim RowCount As Integer = LocalTable.Rows.Count
'Display the data
DataGridView1.DataSource = LocalTable
End Sub
Private Function GetGroupID(InputName As String) As String
'Are you sure member_group_id is a String? Sure looks like it should be an Integer
Dim member_group_id As String = ""
'You can pass the connection string directly to the constructor of the connection
Using MysqlConn As New MySqlConnection(ConnString)
'If you only need the value of one field Select just the field not *
'ALWAYS use parameters. See comment by #djv concerning drop table
Using cmd As New MySqlCommand("SELECT g_id FROM core_members where name= #Name")
'The parameters are interperted by the server as a value and not executable code
'so even if a malicious user entered "drop table" it would not be executed.
cmd.Parameters.Add("#Name", MySqlDbType.VarChar).Value = InputName
MysqlConn.Open()
'ExecuteScalar returns the first column of the first row of the result set
member_group_id = cmd.ExecuteScalar.ToString
End Using
End Using
Return member_group_id
End Function
Private Function GetLicenseKeysData(InputName As String) As DataTable
Dim dt As New DataTable
Using cn As New MySqlConnection(ConnString)
Using cmd As New MySqlCommand("SELECT * FROM `nexus_licensekeys` where lkey_key= #Name;", cn)
cmd.Parameters.Add("#Name", MySqlDbType.VarChar).Value = InputName
cn.Open()
dt.Load(cmd.ExecuteReader())
End Using
End Using
Return dt
End Function
I have a MySQL database with the columns TIME and METHOD, which have about 15,000+ rows of data. I need to get these columns/rows to display on a DataGridView within a vb.net form. I am using the MySql.Data.dll to connect to the database and run my queries. Below is my current code:
Private Sub RetreiveData() Handles Button.click
Dim dt As New DataTable
Dim connectionString As String = "server=ipaddress;database=debugging;user id=root;password=password;port=3307"
Dim connection As MySqlConnection = New MySqlConnection(connectionString)
Try
connection.Open()
Dim sql As String = String.Format("SELECT time, method FROM test1 WHERE custPin='{0}' AND dataID='{1}' ORDER BY TIME;", customerPin, sessionID)
Dim dAdapter As MySqlDataAdapter = New MySqlDataAdapter(Sql, connection)
dAdapter.Fill(dt)
Catch ex As Exception
MessageBox.Show("ERROR: " & ex.Message & Environment.NewLine & ex.StackTrace & Environment.NewLine)
If connection.State = ConnectionState.Open Then
connection.Close()
End If
End Try
Me.dgvCustomerData.DataSource = dt
connection.Close()
End Sub
Note: "dgvCustomerData" is my DataGridView on my form, and "customerPin"/"sessionID" are retrieved from TextBoxes on my form as well.
I have checked through about 20-30 forum posts that state I should bind my data, or use different styles of data adapters, but none have been able to display my data. I can get it to create the two columns, however, no data is filled in. Any assistance would be very helpful, thanks in advanced.
As part of a project to import data into wordpress via screen scraping I've a database table of old and new URL's stored in a MySQL database. In the example below the ExecuteReader command doesn't appear to be returning any data (-1 rows effected), I've ran the SQL via workbench and that returns data, so it's not the SQL or data in the database.
At other times within the code I've called ExecuteNonQuery() and ExecuteScalar() both without issue (so it isn't the connection string).
Any ideas what to try next?
Dim SQL As String
Dim conn As MySqlConnection = New MySqlConnection(_CONNECTIONSTRING)
SQL = "SELECT OrgURL, NewURL FROM `wp_user`.`tbl_linkdata`"
Try
conn.Open()
Dim cmd As MySqlCommand = New MySqlCommand(SQL, conn)
Dim dr As MySqlDataReader = cmd.ExecuteReader()
While (dr.Read)
LinkHashMap.Add(dr.GetString(0), dr.GetString(1))
End While
Console.ForegroundColor = ConsoleColor.Cyan
Console.WriteLine("The Hash map contains " + dr.RecordsAffected + " rows")
dr.Close()
Catch ex As Exception
Console.ForegroundColor = ConsoleColor.Red
Console.WriteLine("Exception loading the hashtable : " + ex.Message)
Finally
conn.Dispose()
End Try
DataReader.RecordsAffected always returns -1 for a SELECT command. What does LinkHashMap.Count return? In MySqlDataReader it is the same:
"The number of rows changed, inserted, or deleted. -1 for SELECT
statements"
If you want to count the number of records you can use LinkHashMap.Count.
You: "LinkHashMap is "Nothing" "
How do you want to add something to it without initializing it first? A NullReferenceException should have happened. So initialize the dictionary (or whatever it is) first via constructor:
Dim LinkHashMap As New Dictionary(Of String, String)
While (dr.Read)
LinkHashMap.Add(dr.GetString(0), dr.GetString(1))
End While
Why won't this delete the data in my MySQL database!?
Private Sub Button4_Click(sender As System.Object, e As System.EventArgs) Handles Button4.Click
Dim dbCon As MySqlConnection
Dim strQuery As String = ""
Dim SQLCmd As MySqlCommand
Dim DR As MySqlDataReader
Try
dbCon = New MySqlConnection("Server=Localhost;Database=myusers;Uid=root;Pwd=Mypassword")
strQuery = "DELETE settings FROM settings WHERE user=" & Me.loginuser.Text
'* FROM settings WHERE user = "Testuser"'
SQLCmd = New MySqlCommand(strQuery, dbCon)
' OPEN THE DB AND KICKOFF THE QUERY
dbCon.Open()
DR = SQLCmd.ExecuteReader
While DR.Read
req1.Text = "" And exlink.Text = ""
End While
' DONE! Close DB
DR.Close()
dbCon.Close()
Catch ex As Exception
TextBox8.Text = ("Fail" & vbCrLf & vbCrLf & ex.Message)
End Try
Here is a picture of my database:
Alternatively I could somehow make it replace what is already in the database, in which case please help me with that.
Try
strQuery = "DELETE FROM settings " _
& " WHERE user = '" & Me.loginuser.Text & "'"
but as was stated earlier, you should be using parameterized queries. If you had a user named O'Brien then your query (as composed above) would fail because of the embedded single quote. When you use DELETE, you are deleting entire records and you already specify the table name in the FROM clause.
I will try to change your code in this way
Using con = New MySqlConnection("Server=.....")
con.Open()
Dim sqlText = "DELETE * FROM settings WHERE user = #ulogin"
Using cmd = new MySqlCommand(sqlText, con)
cmd.Parameters.AddWithValue("#ulogin", Me.loginuser.Text)
cmd.ExecuteNonQuery()
End Using
End Using
First and foremost, do not use string concatenation to create command texts to pass to the database engine. In that way you risk Sql Injections, also, if the user name contains a single quote (i.e. O'Hara) your code will fail with a syntax error (Same problems arise for date formatting, parsing numeric decimals and other globalization issues). Instead a parametrized query like the one in code above will avoid all of these problems.
In a parametrized query, the text of the query doesn't contains the actual value for the search condition or the update or insert data. Instead it contains placeholders ( in our case it is called #ulogin). The correct value to insert at the placeholders position is specified using one or more MySqlParameter added to the Parameters collection of the MySqlCommand. In this case I have used the AddWithValue method that derives the correct datatype directly from the datatype of the value. Because Me.loginuser.Text is a string value then the parameter will be treated as a string value replacing incorrect single quotes and removing extraneus characters usually used to Mount Sql Injections Attacks. The engine will do the rest inserting the correct value at the placeholder at execution time
EDIT: Seeing your comment about the MySql connector used, I will try to update my answer to show a semi-equivalent version for NET 1.
Try
Dim con As MySqlConnection = New MySqlConnection("Server=.....")
con.Open()
Dim sqlText as String = "DELETE * FROM settings WHERE user = #ulogin"
Dim cmd As MySqlCommand = new MySqlCommand(sqlText, con)
Dim par As MySqlParameter = New MySqlParameter("#ulogin", MySqlDbType.VarChar)
par.Value = Me.loginuser.Text
cmd.Parameters.Add(par)
cmd.ExecuteNonQuery()
Finally
con.Close()
End Try
I am not sure if the connector 1.0.10 supports the parameter name with the # prefix or just the : prefix
i dont think you can use double quotes in mysql, i think its single quotes only. try
Query = "DELETE * FROM settings WHERE user = '" & Me.loginuser.Text & "'"