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C# Winform - OracleDataAdapter not persisting the records immediately

I am making changes in an old C# WinForm application.
In the code below, when the DoWork() function is invoked. It calls the two functions PerformOperation1 and PerformOperation2. Both functions have a very similar body. The only difference is that they both update different fields of the same database table.
Finally, when they both have performed their job, we fetch the records using an OracleDataAdapter.
The count of the rows returned is 0 in the code. However, if I execute the query on the database straight away, it returns some rows. This means somehow the records updated by the PerformOperation2 are not pushed to the database at the time when we call the Fill on the DataAapter.
public void DoWork()
{
PerformOperation1();
PerformOperation2();
var sql = "select * from results where result_id = 1 and is_valid = 'Y'";
var table = new DataTable();
var data = new OracleDataAdapter(new OracleCommand(sql, base.Connection));
data.Fill(table);
var count = data.Rows.Count; //It returns 0 But when execute the same query on database, it returns rows.
}
public void PerformOperation1()
{
string sql = "select seq_1, product, count_1, count_2 from results where result_id = 1";
string updateSQL = "update results set count_1 = :count_1, count_2 = :count_2 WHERE seq_1 = :seq_1";
var selectCmd = new OracleCommand(sql, base.Connection);
selectCmd.CommandType = CommandType.Text;
var adapter = new OracleDataAdapter(lCmd);
adapter.UpdateCommand = new OracleCommand(updateSQL, base.Connection);
adapter.UpdateCommand.CommandType = CommandType.Text;
AddCommandParameter(adapter.UpdateCommand, ":count_1", DbType.Double, 11, "count_1");
AddCommandParameter(adapter.UpdateCommand, ":count_2", DbType.Double, 11, "count_2");
var data = new DataSet();
adapter.Fill(data);
foreach (var row in data.Tables[0].Rows)
{
row["count_1"] = GetCount1(row["seq1"]); //Returns Count1
row["count_2"] = GetCount2(row["seq1"]); //Returns Count2
//Forces an immediate garbage collection of all generations
GC.Collect();
GC.WaitForPendingFinalizers();
}
adapter.Update(data);
data.AcceptChanges();
}
public void PerformOperation2()
{
string sql = "select seq_1, product, is_valid from results where result_id = 1";
string updateSQL = "update results set is_valid = :is_valid WHERE seq_1 = :seq_1";
//Does exactly the samething like PerformOperation1 function above.
//100% same code.
//Only difference is that it updates different column named is_valid (with value 'Y' or 'N')
}
public void AddCommandParameter(DbCommand aoCommand, string asParamName, DbType aoDataType, int aiSize, string asColName)
{
if (aoCommand is OracleCommand)
{
OracleCommand loCommand = (OracleCommand)aoCommand;
OracleType loOraDataType = ConvertToOracleType(aoDataType);
loCommand.Parameters.Add(asParamName, loOraDataType, aiSize, asColName);
}
}
Any idea why this is happening, please?

I figured it out. It was not a coding issue. It was some underlying database view problem.

how to Sql Table Data using in switch statement?

I have a table in the SQL database with two columns. I want to use that data in a switch case loop as
switch(Inputvalue) {
case row1.column1:
return row1.column2;
case row2.column1:
return row2.column2;
.
.
.
case rowN.column1:
return rowN.column2;
}
if possible in view using javascript or else in controller using c#
so the program for switch loop is like
switch(Inputvalue) {
case 1:
return Hyderabad;
case 2:
return Chennai;
case 3:
return Banglore;

The question is strange, basically you are asking for a method that returns the name of a city from your table with a given ID. So why don't you use sql as tagged? Presuming sql-server:
public static string GetCityName(int cityId)
{
string sql = "SELECT Name FROM City WHERE Id = #Id";
using(var con = new SqlConnection("Insert Your Connection String"))
{
using(var cmd = new SqlCommand(sql, con))
{
con.Open();
cmd.Parameters.Add("Id", SqlDbType.Int).Value = cityId;
string name = (string) cmd.ExecuteScalar();
return name;
}
}
}

i think it is useful for you
CASE expression
WHEN value_1 THEN result_1
WHEN value_2 THEN result_2
...
WHEN value_n THEN result_n
ELSE result
END

There is no way to do it with Switch-Case, instead of it you can use dictionary for lookup like below:
var lookUp = yourDataTable.AsEnumrable().ToDictionary(r => r.column1, k => k.column2);
var result = lookUp[value];

C# MySQL adding multiple of the same parameter with a loop

Update: as the original question was essentially answered, I've marked this as complete.
I have a C# project in which I'd like to query a database. The SQL query will SELECT from a table, and in the WHERE clause I want to filter the results from a pre-defined list of values specified in C#.
List<string> productNames = new List<string >() { "A", "B", "C" };
foreach (name in productNames)
{
string query = #"
SELECT *
FROM products
WHERE name IN (#name);";
// Execute query
MySqlCommand cmd = new MySqlCommand(query, dbConn);
cmd.Parameters.AddWithValue("name", name);
MySqlDataReader row = cmd.ExecuteReader();
while (row.Read())
{
// Process result
// ...
}
}
However I'm getting an error:
There is already an open DataReader associated with this Connection
which must be closed first
Is it not possible then to use a for loop to add parameters this way to a SELECT statement?

You need to dispose your object to not get the exception. However you don't need to iterate over values and run a query for every value in the list. Try the following code. It makes a parameter for every value and adds it to command to use in "IN (...)" clause.
Also "using" keywords handles disposing objects.
List<string> productsIds = new List<string>() { "23", "46", "76", "88" };
string query = #"
SELECT *
FROM products
WHERE id IN ({0});";
// Execute query
using (MySqlCommand cmd = new MySqlCommand(query, dbConn))
{
int index = 0;
string sqlWhere = string.Empty;
foreach (string id in productsIds)
{
string parameterName = "#productId" + index++;
sqlWhere += string.IsNullOrWhiteSpace(sqlWhere) ? parameterName : ", " + parameterName;
cmd.Parameters.AddWithValue(parameterName, id);
}
query = string.Format(query, sqlWhere);
cmd.CommandText = query;
using (MySqlDataReader row = cmd.ExecuteReader())
{
while (row.Read())
{
// Process result
// ...
}
}
}

You are doing few things wrong. Let me point out them:
Everything is fine in the first iteration of the loop, when you are in second iteration the First Reader associated with the command remains opened and that result in current error.
You are using Where IN(..) you you can specify the values within IN as comma separated so there is no need to iterate through parameters.
You can use String.Join method to construct this values with a comma separator.
Now take a look into the following code:
List<int> productsIds = new List<int>() { 23, 46, 76, 88 };
string idInParameter = String.Join(",", productsIds);
// Create id as comma separated string
string query = "SELECT * FROM products WHERE id IN (#productId);";
MySqlCommand cmd = new MySqlCommand(query, dbConn);
cmd.Parameters.AddWithValue("#productId", idInParameter);
MySqlDataReader row = cmd.ExecuteReader();
while (row.Read())
{
// Process result
// ...
}
Please note if the id field in the table is not integers then you have to modify the construction of idInParameter as like the following:
idInParameter = String.Join(",", productsIds.Select(x => "'" + x.ToString() + "'").ToArray());

Pass the comma separated productIds string instead of looping. Read more about IN here.
string productIdsCommaSeparated = string.Join(",", productsIds.Select(n => n.ToString()).ToArray())
string query = #"
SELECT *
FROM products
WHERE id IN (#productId);";
// Execute query
MySqlCommand cmd = new MySqlCommand(query, dbConn);
cmd.Parameters.AddWithValue("productId", productIdsCommaSeparated );
MySqlDataReader row = cmd.ExecuteReader();
while (row.Read())
{
// Process result
// ...
}
The error you are getting is because you do not close the MySqlDataReader. You must close it to get rid of error before you call ExecuteReader in next iteration but this is not proper way in this case.

From what I tried and tested seems best solution (especially for text column types) is to create a list of individual parameters and add it as a range the to the query and parameters.
e.g:
List<MySqlParameter> listParams = new List<MySqlParameter>();
for (int i = 0; i < listOfValues.Length; i++)
{
listParams.Add(new MySqlParameter(string.Format("#values{0}", i),
MySqlDbType.VarChar) { Value = listOfValues[i] });
}
string sqlCommand = string.Format("SELECT data FROM table WHERE column IN ({0})",
string.Join(",", listParams.Select(x => x.ParameterName)));
......
using (MySqlCommand command = new MySqlCommand(sqlCommand, connection)
{
............
command.Parameters.AddRange(listParams.ToArray());
............
}

database schema has changed

I keep getting this error database schema has changed near "1": syntax error.
I am not changing my schema in the code.
This is the code where I make the schema.
wish to try each answer in order that you posted it.
This code is used to transfer a database to another database program.
So it has to be compatible with more then one database program.
public DataTable GetSchemaTable(string schema, string nameTable)
{
switch (m_dbType)
{
case dbTypeEnum.Sqlite:
//Make the schema of the source table
MakeConnectionString();
string fullTableName = schema.Length > 0
? string.Format("[{0}].[{1}]", schema, nameTable)
: string.Format("[{0}]", nameTable);
if (!string.IsNullOrEmpty(fullTableName))
{
string sql = string.Format("SELECT * FROM {0} LIMIT 1", fullTableName);
DataTable dtSchemaSource;
try
{
using (IDataReader rdr = ReadOnlyForwardOnly(sql))
{
dtSchemaSource = rdr.GetSchemaTable();
}
}
finally
{
CloseConnection();
}
if (dtSchemaSource == null)
{
throw new RadGeneralException("rdr.GetSchemaTable() returns null with sql = " + sql);
}
return dtSchemaSource;
}
break;
default:
//Make the schema of the source table
MakeConnectionString();
string fullTableName = schema.Length > 0
? string.Format("[{0}].[{1}]", schema, nameTable)
: string.Format("[{0}]", nameTable);
string sql = string.Format("SELECT TOP 1 * FROM {0}", fullTableName);
DataTable dtSchemaSource;
try
{
using (IDataReader rdr = ReadOnlyForwardOnly(sql))
{
dtSchemaSource = rdr.GetSchemaTable();
}
}
finally
{
CloseConnection();
}
if (dtSchemaSource == null)
{
throw new RadGeneralException("rdr.GetSchemaTable() returns null with sql = " + sql);
}
return dtSchemaSource;
}
}
This is the part where the sqlite schema has changed arror occurs.
StringBuilder sbColList = new StringBuilder();
nCol = 0;
identityColInBothTables = false;
//Make the schema of the source table
DataTable dtSchemaSource = objDbSource.GetSchemaTable(SchemaSource, Name);
//Make the schema of the target table
DataTable dtSchemaTarget = objDbTarget.GetSchemaTable(SchemaTarget, Name);

I believe that instead of SELECT TOP 1 * you need to be using SELECT * FROM .... LIMIT 1

You need to check nameTable is null or empty
if(!string.IsNullOrEmpty(fullTableName))
string sql = string.Format("SELECT * FROM {0} LIMIT 1", fullTableName);
for SQLLITE
SELECT * FROM Table_Name LIMIT 1;
for SQL
SELECT TOP 1 * FROM Table_Name;

Can you try this:
SELECT * FROM SAMPLE_TABLE ORDER BY ROWID ASC LIMIT 1

Fastest way to update more than 50.000 rows in a mdb database c#

I searched on the net something but nothing really helped me. I want to update, with a list of article, a database, but the way that I've found is really slow.
This is my code:
List<Article> costs = GetIdCosts(); //here there are 70.000 articles
conn = new OleDbConnection(string.Format(MDB_CONNECTION_STRING, PATH, PSW));
conn.Open();
transaction = conn.BeginTransaction();
using (var cmd = conn.CreateCommand())
{
cmd.Transaction = transaction;
cmd.CommandText = "UPDATE TABLE_RO SET TABLE_RO.COST = ? WHERE TABLE_RO.ID = ?;";
for (int i = 0; i < costs.Count; i++)
{
double cost = costs[i].Cost;
int id = costs[i].Id;
cmd.Parameters.AddWithValue("data", cost);
cmd.Parameters.AddWithValue("id", id);
if (cmd.ExecuteNonQuery() != 1) throw new Exception();
}
}
transaction.Commit();
But this way take a lot of minutes something like 10 minutes or more. There are another way to speed up this updating ? Thanks.

Try modifying your code to this:
List<Article> costs = GetIdCosts(); //here there are 70.000 articles
// Setup and open the database connection
conn = new OleDbConnection(string.Format(MDB_CONNECTION_STRING, PATH, PSW));
conn.Open();
// Setup a command
OleDbCommand cmd = new OleDbCommand();
cmd.Connection = conn;
cmd.CommandText = "UPDATE TABLE_RO SET TABLE_RO.COST = ? WHERE TABLE_RO.ID = ?;";
// Setup the paramaters and prepare the command to be executed
cmd.Parameters.Add("?", OleDbType.Currency, 255);
cmd.Parameters.Add("?", OleDbType.Integer, 8); // Assuming you ID is never longer than 8 digits
cmd.Prepare();
OleDbTransaction transaction = conn.BeginTransaction();
cmd.Transaction = transaction;
// Start the loop
for (int i = 0; i < costs.Count; i++)
{
cmd.Parameters[0].Value = costs[i].Cost;
cmd.Parameters[1].Value = costs[i].Id;
try
{
cmd.ExecuteNonQuery();
}
catch (Exception ex)
{
// handle any exception here
}
}
transaction.Commit();
conn.Close();
The cmd.Prepare method will speed things up since it creates a compiled version of the command on the data source.

Small change option:
Using StringBuilder and string.Format construct one big command text.
var sb = new StringBuilder();
for(....){
sb.AppendLine(string.Format("UPDATE TABLE_RO SET TABLE_RO.COST = '{0}' WHERE TABLE_RO.ID = '{1}';",cost, id));
}
Even faster option:
As in first example construct a sql but this time make it look (in result) like:
-- declaring table variable
declare table #data (id int primary key, cost decimal(10,8))
-- insert union selected variables into the table
insert into #data
select 1121 as id, 10.23 as cost
union select 1122 as id, 58.43 as cost
union select ...
-- update TABLE_RO using update join syntax where inner join data
-- and copy value from column in #data to column in TABLE_RO
update dest
set dest.cost = source.cost
from TABLE_RO dest
inner join #data source on dest.id = source.id
This is the fastest you can get without using bulk inserts.

Performing mass-updates with Ado.net and OleDb is painfully slow. If possible, you could consider performing the update via DAO. Just add the reference to the DAO-Library (COM-Object) and use something like the following code (caution -> untested):
// Import Reference to "Microsoft DAO 3.6 Object Library" (COM)
string TargetDBPath = "insert Path to .mdb file here";
DAO.DBEngine dbEngine = new DAO.DBEngine();
DAO.Database daodb = dbEngine.OpenDatabase(TargetDBPath, false, false, "MS Access;pwd="+"insert your db password here (if you have any)");
DAO.Recordset rs = daodb.OpenRecordset("insert target Table name here", DAO.RecordsetTypeEnum.dbOpenDynaset);
if (rs.RecordCount > 0)
{
rs.MoveFirst();
while (!rs.EOF)
{
// Load id of row
int rowid = rs.Fields["Id"].Value;
// Iterate List to find entry with matching ID
for (int i = 0; i < costs.Count; i++)
{
double cost = costs[i].Cost;
int id = costs[i].Id;
if (rowid == id)
{
// Save changed values
rs.Edit();
rs.Fields["Id"].Value = cost;
rs.Update();
}
}
rs.MoveNext();
}
}
rs.Close();
Note the fact that we are doing a full table scan here. But, unless the total number of records in the table is many orders of magnitude bigger than the number of updated records, it should still outperform the Ado.net approach significantly...