Develop Reference

Datarow id string not matching with object id string even though they are identical strings after checking debug

I am trying to search through a list of ID strings in my database where an ID string is equal to the one of the object i am trying to create. The id being created is in a factory design pattern where a train type "express" is made with an ID of "1E45". After this ID is created, it increments the number section after the letter and then that can be used for the next train added.
When searching through the list with a foreach it returns the id from the database that is similar to the one trying to be created.
But when I try to match these two after using toString to change them both and match in an IF. The match returns false even though when I check the debug it is exactly the same?
It then just continues on to try and add a new object with that ID that already exists and crashes.
What am I doing wrong? it doesn't make sense after checking the values being matched and it saying false.
Here is the code I have set up:
//Create sql command variables to create new commands
SqlCommand insert = new SqlCommand();
SqlCommand checkID = new SqlCommand();
//Set the command type to text
insert.CommandType = CommandType.Text;
checkID.CommandType = CommandType.Text;
//Searches for an ID in the database that matches one that is trying to be created
checkID.CommandText = "SELECT id FROM Train WHERE id = #trainID";
//Parameters for checking ID in database
checkID.Parameters.AddWithValue("#trainID", train.TrainID);
//Set the connection for the command for the checkID sql connection
checkID.Connection = con;
//Start the connection
con.Open();
DataTable dt = new DataTable();
SqlDataAdapter adapter = new SqlDataAdapter(checkID);
adapter.Fill(dt);
dt.Load(checkID.ExecuteReader());
//Item last = Module.
foreach (DataRow i in dt.Rows)
{
if (i.ToString() == train.TrainID.ToString())
{
MessageBox.Show("This ID already exists! " + train.TrainID);
return;
}
}
//Close the connection
con.Close();
//Set the text for the command to insert data to the database connected to
insert.CommandText = "INSERT Train (id, departure, destination, type, intermediate, departure_time, departure_date, sleeperBerth, firstClass) " +
"VALUES ( #trainID , #departure, #destination, #type, #intermediate, #dep_time, #dep_date, #sleep, #first)";
//Parameters for adding values from the train object to the database
insert.Parameters.AddWithValue("#trainID", train.TrainID);
insert.Parameters.AddWithValue("#departure", train.Departure);
insert.Parameters.AddWithValue("#destination", train.Destination);
insert.Parameters.AddWithValue("#type", train.Type);
insert.Parameters.AddWithValue("#intermediate", intStops);
insert.Parameters.AddWithValue("#dep_time", train.DepartureTime);
insert.Parameters.AddWithValue("#dep_date", train.DepartureDay);
insert.Parameters.AddWithValue("#sleep", train.SleeperBerth);
insert.Parameters.AddWithValue("#first", train.FirstClass);
//Set the connection for the command for the insert sql connection
insert.Connection = con;
//Start the connection
con.Open();
//Execute the command specified
insert.ExecuteNonQuery();
//Close the connection
con.Close();

Sounds like you need to change your column id in the table train to an IDENTITY column, and let the database handle the ID assignment:
ALTER TABLE dbo.Train ALTER COLUMN id int IDENTITY(1,1); --data type guessed
Then, in your application, you don't need to generate a value for ID, nor do declare it in your INSERT statement (either in the list of columns to INSERT into or in your VALUES clause).

Using OleDbDataAdapter to update a DataTable C#

I have been trying to use OleDbDataAdapter to update a DataTable but got confused about the commands.
Since I sometimes get info from diffrent tables I can't use a CommandBuilder.
So I have tried to create the commands on my on but found it hard with the parameters.
DataTable.GetChanges returns rows that needs to use an INSERT or an UPDATE command - I guess I can't distinct between them.
I need you to complete the following:
DataTable dt = new DataTable();
OleDbDataAdapter da = new OleDbDataAdapter();
// Here I create the SELECT command and pass the connection.
da.Fill(dt);
// Here I make changes (INSERT/UPDATE) to the DataTable (by a DataGridView).
da.UpdateCommand = new OleDbCommand("UPDATE TABLE_NAME SET (COL1, COL2, ...) VALUES (#newVal1, #newVal2, ...) WHERE id=#id"); // How can I use the values of the current row (that the da is updating) as the parameters (#newVal1, #newVal2, id....)?
Thank you very much!

The data adapter can work in conjunction with the datatable. As such, I've actually wrapped mine together into a class and works quite well. Aside from the complexities of my stuff, here's a snippet that might help you along. When adding a parameter, you can identify the column source that the data is coming from FROM the DataTable. This way, when a record is internally identified as "Added" or "Updated" (or "Deleted"), when you build your SQL Insert/Update/Delete commands, it will pull the data from the columns from the respective rows.
For example. Say I have a DataTable, primary Key is "MyID" and has columns "ColX, ColY, ColZ". I create my DataAdapter and build out my select, update, delete commands something like... (? is a place-holder for the parameters)
DataAdapter myAdapter = new DataAdapter()
myAdapter.SelectCommand = new OleDbCommand();
myAdapter.InsertCommand = new OleDbCommand();
myAdapter.UpdateCommand = new OleDbCommand();
myAdapter.DeleteCommand = new OleDbCommand();
myAdapter.SelectCommand.CommandText = "select * from MyTable where MyID = ?";
myAdapter.InsertCommand.CommandText = "insert into MyTable ( ColX, ColY, ColZ ) values ( ?, ?, ? )";
myAdapter.UpdateCommand.CommandText = "update MyTable set ColX = ?, ColY = ?, ColZ = ? where MyID = ?";
myAdapter.DeleteCommand.CommandText = "delete from MyTable where MyID = ?";
Now, each has to have their respective "Parameters". The parameters have to be addded in the same sequence as their corresponding "?" place-holders.
// Although I'm putting in bogus values for preparing the parameters, its just for
// data type purposes. It does get changed through the data adapter when it applies the changes
OleDbParameter oParm = new OleDbParameter( "myID", -1 );
oParm.DbType = DbType.Int32;
oParm.SourceColumn = "myID"; // <- this is where it looks back to source table's column
oParm.ParameterName = "myID"; // just for consistency / readability reference
myAdapter.SelectCommand.Parameters.Add( oParm );
do similar for rest of parameters based on their types... char, int, double, whatever
Again, I have like a wrapper class that handles managment on a per-table basis... in brief
public myClassWrapper
{
protected DataTable myTable;
protected DataAdapter myAdapter;
... more ...
protected void SaveChanges()
{
}
}
Its more complex than just this, but during the "SaveChanges", The datatable and dataAdapter are in synch for their own purposes. Now, flushing the data. I check for the status of the table and then you can pass the entire table to the dataAdapter for update and it will cycle through all changed records and push respective changes. You'll have to trap for whatever possible data errors though.
myAdapter.Update( this.MyTable );
As it finds each "changed" record, it pulls the values from the Column Source as identified by the parameter that is found in the table being passed to the adapter for processing.
Hopefully this has given you a huge jump on what you are running into.
---- COMMENT PER FEEDBACK ----
I would put your update within a try/catch, and step into the program to see what the exception is. The message adn/or inner exception of the error might give more info. However, try to simplify your UPDATE to only include a FEW fields with the WHERE "Key" element.
Additionally, and I oopsed, missed this from first part answer. You might have to identify the datatable's "PrimaryKey" column. To do so, its a property of the DataTable that expects and array of columns that represent the primary key for the table. What I did was...
// set the primary key column of the table
DataColumn[] oCols = { myDataTbl.Columns["myID"] };
myDataTbl.PrimaryKey = oCols;
I would comment out your full update string and all its parameters for your UPDATE. Then, build it with just as simple as my sample of only setting 2-3 columns and the where clause
myAdapter.UpdateCommand.CommandText = "update MyTable set ColX = ?, ColY = ? where MyID=?";
Add Parameter object for "X"
Add Parameter object for "Y"
Add Parameter object for "MyID"
Pick fields like int or char so they have the least probability of problems for data type conversions, then, once that works, try adding all your "int" and "character" columns... then add any others. Also, which database are you going against. SOME databases don't use "?" as placeholder in the command but use "named" parameters, some using
"actualColumn = #namedCol"
or even
"actualColumn = :namedCol"
Hope this gets you over the hump...

You could use the String.Format Method to replace the #newVal1, #newVal2, ... in your code, like this da.UpdateCommand = new OleDbCommand(String.Format("UPDATE TABLE_NAME SET (COL1, COL2, ...) VALUES ({0}, {1}, ...) WHERE id=#id",OBJECT_ARRAY_CONTAINING_VALUES_FROM_THEDG));
[Eidt per comment]
To handle the row[0], row[1] you need a loop like:
for(i=0; i<rows.Count; i++)
{
da.UpdateCommand = new OleDbCommand(String.Format("UPDATE...",row[i]);
da.Update(dt);
}

C# , SQL update multiple rows

i have a question regarding an efficient way to update multiple rows via SQL.
Basiclly i have a query i need to run on different RowIDs:
UPDATE TableName SET Column = (some number) WHERE RowID = (some number)
if to be more specific this is a better example:
UPDATE TableName SET Column = 5 WHERE RowID = 1000
UPDATE TableName SET Column = 10 WHERE RowID = 1001
UPDATE TableName SET Column = 30 WHERE RowID = 1002
..
I'd like to know how should i build the update query command on C# (or just give me an example of the resulted query i should get to) so once i use ExecuteQuery it will run all of these commands at one piece and not by executing each command.
edited:
I have another problem, can you also explain what about dynamic situation in which not necessarly the row i want to update exist already, in that case i need to insert instead of update. to explain better, back to my example lets say i want to do
UPDATE TableName SET Column = 5 WHERE RowID = 1000
INSERT INTO TableName [RowID, Column] VALUES (1001, 20)
UPDATE TableName SET Column = 30 WHERE RowID = 1002
..
The meaning of this is that i need to check if the row exist, if so i'd use update otherwise i'll have to insert it.
Thank you!

You could use a DataTable to store your records, insert, delete or change rows and update all changes in one batch by using SqlDataAdapter's UpdateBatchSize(0 means no limit):
public static void BatchUpdate(DataTable dataTable,Int32 batchSize)
{
// Assumes GetConnectionString() returns a valid connection string.
string connectionString = GetConnectionString();
// Connect to the AdventureWorks database.
using (SqlConnection connection = new
SqlConnection(connectionString))
{
// Create a SqlDataAdapter.
SqlDataAdapter adapter = new SqlDataAdapter();
// Set the UPDATE command and parameters.
adapter.UpdateCommand = new SqlCommand(
"UPDATE Production.ProductCategory SET "
+ "Name=#Name WHERE ProductCategoryID=#ProdCatID;",
connection);
adapter.UpdateCommand.Parameters.Add("#Name",
SqlDbType.NVarChar, 50, "Name");
adapter.UpdateCommand.Parameters.Add("#ProdCatID",
SqlDbType.Int, 4, "ProductCategoryID");
adapter.UpdateCommand.UpdatedRowSource = UpdateRowSource.None;
// Set the INSERT command and parameter.
adapter.InsertCommand = new SqlCommand(
"INSERT INTO Production.ProductCategory (Name) VALUES (#Name);",
connection);
adapter.InsertCommand.Parameters.Add("#Name",
SqlDbType.NVarChar, 50, "Name");
adapter.InsertCommand.UpdatedRowSource = UpdateRowSource.None;
// Set the DELETE command and parameter.
adapter.DeleteCommand = new SqlCommand(
"DELETE FROM Production.ProductCategory "
+ "WHERE ProductCategoryID=#ProdCatID;", connection);
adapter.DeleteCommand.Parameters.Add("#ProdCatID",
SqlDbType.Int, 4, "ProductCategoryID");
adapter.DeleteCommand.UpdatedRowSource = UpdateRowSource.None;
// Set the batch size.
adapter.UpdateBatchSize = batchSize;
// Execute the update.
adapter.Update(dataTable);
}
}
http://msdn.microsoft.com/en-us/library/aadf8fk2.aspx
I assume you're misunderstanding how the dbms works internally. This
UPDATE TableName SET Column = 5 WHERE RowID = 1000;
UPDATE TableName SET Column = 5 WHERE RowID = 1002;
is the same as
UPDATE TableName SET Column = 5 WHERE RowID IN(1000,2002);
The dbms will update all affected records one by one anyway even if you would write a statement like UPDATE table SET value=1 which would affect every record in the table. By updating in one batch you ensure that all updates(deletes,inserts)are submitted to the database instead of one roundtrip for every statement.

Use MERGE:
MERGE INTO TableName
USING (
VALUES (1000, 5),
(1001, 10),
(1002, 30)
) AS source (RowID, Column_name)
ON TableName.RowID = source.RowID
WHEN MATCHED THEN
UPDATE
SET Column_name = source.Column_name
WHEN NOT MATCHED THEN
INSERT (RowID, Column_name)
VALUES (RowID, Column_name);
Rather than hard-coding/dynamic SQL, the MERGE statement could be encapsulated into a stored proc that takes a table-valued parameter.

Getting the Last Insert ID with SQLite.NET in C#

I have a simple problem with a not so simple solution... I am currently inserting some data into a database like this:
kompenzacijeDataSet.KompenzacijeRow kompenzacija = kompenzacijeDataSet.Kompenzacije.NewKompenzacijeRow();
kompenzacija.Datum = DateTime.Now;
kompenzacija.PodjetjeID = stranka.id;
kompenzacija.Znesek = Decimal.Parse(tbZnesek.Text);
kompenzacijeDataSet.Kompenzacije.Rows.Add(kompenzacija);
kompenzacijeDataSetTableAdapters.KompenzacijeTableAdapter kompTA = new kompenzacijeDataSetTableAdapters.KompenzacijeTableAdapter();
kompTA.Update(this.kompenzacijeDataSet.Kompenzacije);
this.currentKompenzacijaID = LastInsertID(kompTA.Connection);
The last line is important. Why do I supply a connection? Well there is a SQLite function called last_insert_rowid() that you can call and get the last insert ID. Problem is it is bound to a connection and .NET seems to be reopening and closing connections for every dataset operation. I thought getting the connection from a table adapter would change things. But it doesn't.
Would anyone know how to solve this? Maybe where to get a constant connection from? Or maybe something more elegant?
Thank you.
EDIT:
This is also a problem with transactions, I would need the same connection if I would want to use transactions, so that is also a problem...

Using C# (.net 4.0) with SQLite, the SQLiteConnection class has a property LastInsertRowId that equals the Primary Integer Key of the most recently inserted (or updated) element.
The rowID is returned if the table doesn't have a primary integer key (in this case the rowID is column is automatically created).
See https://www.sqlite.org/c3ref/last_insert_rowid.html for more.
As for wrapping multiple commands in a single transaction, any commands entered after the transaction begins and before it is committed are part of one transaction.
long rowID;
using (SQLiteConnection con = new SQLiteConnection([datasource])
{
SQLiteTransaction transaction = null;
transaction = con.BeginTransaction();
... [execute insert statement]
rowID = con.LastInsertRowId;
transaction.Commit()
}

select last_insert_rowid();
And you will need to execute it as a scalar query.
string sql = #"select last_insert_rowid()";
long lastId = (long)command.ExecuteScalar(sql); // Need to type-cast since `ExecuteScalar` returns an object.

last_insert_rowid() is part of the solution. It returns a row number, not the actual ID.
cmd = CNN.CreateCommand();
cmd.CommandText = "SELECT last_insert_rowid()";
object i = cmd.ExecuteScalar();
cmd.CommandText = "SELECT " + ID_Name + " FROM " + TableName + " WHERE rowid=" + i.ToString();
i = cmd.ExecuteScalar();

I'm using Microsoft.Data.Sqlite package and I do not see a LastInsertRowId property. But you don't have to create a second trip to database to get the last id. Instead, combine both sql statements into a single string.
string sql = #"
insert into MyTable values (null, #name);
select last_insert_rowid();";
using (var cmd = conn.CreateCommand()) {
cmd.CommandText = sql;
cmd.Parameters.Add("#name", SqliteType.Text).Value = "John";
int lastId = Convert.ToInt32(cmd.ExecuteScalar());
}

There seems to be answers to both Microsoft's reference and SQLite's reference and that is the reason some people are getting LastInsertRowId property to work and others aren't.
Personally I don't use an PK as it's just an alias for the rowid column. Using the rowid is around twice as fast as one that you create. If I have a TEXT column for a PK I still use rowid and just make the text column unique. (for SQLite 3 only. You need your own for v1 & v2 as vacuum will alter rowid numbers)
That said, the way to get the information from a record in the last insert is the code below. Since the function does a left join to itself I LIMIT it to 1 just for speed, even if you don't there will only be 1 record from the main SELECT statement.
SELECT my_primary_key_column FROM my_table
WHERE rowid in (SELECT last_insert_rowid() LIMIT 1);

The SQLiteConnection object has a property for that, so there is not need for additional query.
After INSERT you just my use LastInsertRowId property of your SQLiteConnection object that was used for INSERT command.
Type of LastInsertRowId property is Int64.
Off course, as you already now, for auto increment to work the primary key on table must be set to be AUTOINCREMENT field, which is another topic.

database = new SQLiteConnection(databasePath);
public int GetLastInsertId()
{
return (int)SQLite3.LastInsertRowid(database.Handle);
}

# How about just running 2x SQL statements together using Execute Scalar?
# Person is a object that has an Id and Name property
var connString = LoadConnectionString(); // get connection string
using (var conn = new SQLiteConnection(connString)) // connect to sqlite
{
// insert new record and get Id of inserted record
var sql = #"INSERT INTO People (Name) VALUES (#Name);
SELECT Id FROM People
ORDER BY Id DESC";
var lastId = conn.ExecuteScalar(sql, person);
}

In EF Core 5 you can get ID in the object itself without using any "last inserted".
For example:
var r = new SomeData() { Name = "New Row", ...};
dbContext.Add(r);
dbContext.SaveChanges();
Console.WriteLine(r.ID);
you would get new ID without thinking of using correct connection or thread-safety etc.

If you're using the Microsoft.Data.Sqlite package, it doesn't include a LastInsertRowId property in the SqliteConnection class, but you can still call the last_insert_rowid function by using the underlying SQLitePCL library. Here's an extension method:
using Microsoft.Data.Sqlite;
using SQLitePCL;
public static long GetLastInsertRowId(this SqliteConnection connection)
{
var handle = connection.Handle ?? throw new NullReferenceException("The connection is not open.");
return raw.sqlite3_last_insert_rowid(handle);
}

How can I see the data of a SQL server database in c#, and where it's store?

I have a program written in c# visual studio 2008 with SQL server 2005 (.mdf) database.
Here is part of the code:
...
SqlCommandBuilder cb;
cb = new SqlCommandBuilder(dataAdapter);
String[] dataList =new String [8];
...
DataTable resultTable = new DataTable();
FillDataList(data);
dataAdapter = new SqlDataAdapter("insert into ProcessData values('" + dataList[0] + "','" + dataList[1] + "','" + dataList[2] + "','" + dataList[3] + "','" + dataList[4] + "','" + dataList[5] + "','" + dataList[6] + "','" + dataList[7]+"')", con);
dataAdapter.Fill(resultTable);
...
My questions are:
1) Where is the data I added in those lines stored?
2) Why is it that when I Right-Click with the mouse in the Server Explorer->Data Connections->Tables->ProcessData (my table's name)->"show Table Data", I don't see the data but just NULL in the columns, and how can i see the data there?
3) Why when I present this data in a DataGridView sometimes it shows the data and sometimes it doesn't?
Many Thanks!

Without seeing more info on the datalist object and its construction, it's impossible to say. However, you're using the Fill and SQLDataAdapter incorrectly. The FILL relies on the SQLDataAdapter having a SelectCommand property set, which is what your code is bunging the INSERT statement into (that's what the SQLDataAdapter's constructor does). So...your Fill returns nothing as there's no SELECT where there should be.
Your INSERT should be part of the dataadapter's InsertCommand, and you'll need to write a separate SELECT statement to get anything into your resultTable.

I think you need to read some basic documentation on ADO.NET before you write any more code. You're passing an INSERT statement to the SqlDataAdapter constructor, which takes a SELECT statement. You're using the Fill method of SqlDataAdapter where you should be using the Update method. You're building a SQL string with hard-coded values in it where you should be using SqlParameters with references to the DataTable Columns. And is the fact that your DataTable is called "data" but that SQL string is using indexed properties from "dataList" just a typo? Because if it is, DataTable doesn't have an indexed property.

Try doing it like this (you need to fill in the correct connection string though):
// Get the db connection
SqlConnection dbCon = new SqlConnection("connection string");
// Select the data from the database table into a DataSet (even if it's empty)
DataSet myData = new DataSet();
SqlDataAdapter dbAdapter = new SqlDataAdapter("select * from ProcessData", dbCon);
dbAdapter.Fill(myData);
myData.Tables[0].TableName = "ProcessData"; // Keeps the table name consistent for the DataMember property
// Use the command builder to add insert, delete, update commands to your adapter
// You must have a primary key on the table for these to work, though
SqlCommandBuilder dbComBuilder = new SqlCommandBuilder(dbAdapter);
dbAdapter.InsertCommand = dbComBuilder.GetInsertCommand();
dbAdapter.DeleteCommand = dbComBuilder.GetDeleteCommand();
dbAdapter.UpdateCommand = dbComBuilder.GetUpdateCommand();
// Bind the data set to the GridView for viewing / editing
yourGridControl.AutoGenerateColumns = true; // Optional, if you haven't manually added the columns
yourGridControl.DataSource = myData;
yourGridControl.DataMember = "ProcessData";
// Use the db adapter to update the database (by calling those commands) with
// changes made to the DataSet through the grid. This would go in a different
// form event, like a Save Button click.
dbAdapter.Update();
If you don't have a primary key in the ProcessData table, you can directly insert values using this command:
// Insert the data directly with a command
SqlCommand dbInsCommand = new SqlCommand("insert into ProcessData values (" + val1 + "," + val2 + ")", dbCon);
dbInsCommand.ExecuteNonQuery();