Develop Reference

Setting up a chart that displays the number of times a dataset record appears in C#

I am trying to create a chart that when, at the push of a button displays a chart that shows the user the number of times a record has appeared in the dataset/table that it is linked to. Please bare in mind that I have little experience with using Charts in Visual Studios/C#.
Currently I am getting this error: Error
This is all the code I have so far:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.OleDb;
namespace RRAS
{
public partial class formRRAS : Form
{
public OleDbConnection DataConnection = new OleDbConnection();
public formRRAS()
{
InitializeComponent();
}
private void formRRAS_Load(object sender, EventArgs e)
{
// TODO: This line of code loads data into the 'database1DataSet.tblReject_test' table. You can move, or remove it, as needed.
this.tblReject_testTableAdapter.Fill(this.database1DataSet.tblReject_test);
}
private void exitToolStripMenuItem_Click(object sender, EventArgs e)
{
this.Close();
}
private void btnSearch_Click(object sender, EventArgs e)
{
//This creates the String Publisher which grabs the information from the combo box on the form.
//Select and Dataconnection are also defined here.
string Select = "SELECT * FROM tblReject_test";
string DataConnection;
string Department = txtDepartment.Text;
string Start_Date = txtStart.Text;
string End_Date = txtEnd.Text;
string Anatomy = txtAnatomy.Text;
string RFR = cmbRFR.Text;
string Comment = txtComment.Text;
//Select defines what should be loaded on to the dataset.
if (Department != "")
{
Select = Select + " WHERE department_id =" + "'" + Department + "'";
if (Anatomy != "")
{
Select = Select + "AND body_part_examined =" + "'" + Anatomy + "'";
if (Start_Date != "")
{
Select = Select + " AND study_date =" + "'" + Start_Date + "'";
if (End_Date != "")
{
Select = Select + " AND study_date =" + "'" + End_Date + "'";
if (RFR != "")
{
Select = Select + " AND reject_category =" + "'" + RFR + "'";
if(Comment != "")
{
Select = Select + " AND reject_comment =" + "'" + Comment + "'";
}
}
}
}
}
}
else
{
Select = "SELECT * FROM tblReject_test";
}
//DataConnection connects to the database.
string connectiontring= "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\\Database1.mdb";
DataConnection = new OleDbConnection(connectiontring);
//The DataAdapter is the code that ensures both the data in the Select and DataConnection strings match.
OleDbDataAdapter rdDataAdapter = new OleDbDataAdapter(Select, DataConnection);
try
{
//It then clears the datagridview and loads the data that has been selected from the DataAdapter.
database1DataSet.tblReject_test.Clear();
rdDataAdapter.Fill(this.database1DataSet.tblReject_test);
}
catch (OleDbException exc)
{
System.Windows.Forms.MessageBox.Show(exc.Message);
}
}
private void btnLoadChart_Click(object sender, EventArgs e)
{
try
{
int count = database1DataSet.Tables["tblReject_test"].Rows.Count;
DataConnection.Open();
OleDbCommand command = new OleDbCommand();
command.Connection = DataConnection;
string query = "SELECT * FROM tblReject_test";
command.CommandText = query;
OleDbDataReader reader = command.ExecuteReader();
while (reader.Read())
{
charRejections.Series["RFR"].Points.AddXY(reader["reject_category"].ToString(), reader[count].ToString());
}
DataConnection.Close();
}
catch (Exception ex)
{
MessageBox.Show("Error " + ex);
}
}
}
}

Your code wouldn't compile as you are assigning a string to DataConnection (instance of OleDbConnection).
The correct usage should be as following.
string connectiontring = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\\Database1.mdb";
DataConnection = new OleDbConnection(connectiontring));
Also, your code doesn't close Database connection in case of exception.
It would be recommended to use the code as shown below. This is taken from MSDN
using (OleDbConnection connection = new OleDbConnection(connectionString))
{
try
{
connection.Open();
Console.WriteLine("DataSource: {0} \nDatabase: {1}",
connection.DataSource, connection.Database);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
// The connection is automatically closed when the
// code exits the using block.
}

make a label static error : cannot access a non-static member of outer type 'windowsForm8.Form1' via nested Type 'windowsForm8.Form1.DBConnect'

Yo this is my first post here and i wanna know how to fix this problem in C#
so im tryin to connect to database and select information from it and those information will be displayed as a label ! easy,
so this is the error i get :
cannot access a non-static member of outer type 'windowsForm8.Form1'
via nested Type 'windowsForm8.Form1.DBConnect'
and this is the Code :
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using MySql.Data.MySqlClient;
namespace WindowsFormsApplication8
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
public class DBConnect
{
private MySqlConnection connection;
private string server;
private string database;
private string uid;
private string password;
//Constructor
public DBConnect()
{
Initialize();
}
//Initialize values
private void Initialize()
{
server = "net";
database = "rainbow";
uid = "ok";
password = "passwd!";
string connectionString;
connectionString = "SERVER=" + server + ";" + "DATABASE=" +
database + ";" + "UID=" + uid + ";" + "PASSWORD=" + password + ";";
connection = new MySqlConnection(connectionString);
}
//open connection to database
private bool OpenConnection()
{
try
{
connection.Open();
return true;
}
catch (MySqlException ex)
{
//When handling errors, you can your application's response based
//on the error number.
//The two most common error numbers when connecting are as follows:
//0: Cannot connect to server.
//1045: Invalid user name and/or password.
switch (ex.Number)
{
case 0:
MessageBox.Show("Cannot connect to server. Contact administrator");
break;
case 1045:
MessageBox.Show("Invalid username/password, please try again");
break;
default :
MessageBox.Show("Connected Successfuly!!");
break;
}
return false;
}
}
//Close connection
private bool CloseConnection()
{
try
{
connection.Close();
return true;
}
catch (MySqlException ex)
{
MessageBox.Show(ex.Message);
return false;
}
}
//Insert statement
public void Insert()
{
string query = "INSERT INTO mytable (username, password) VALUES('shryder', 'nopassword')";
//open connection
if (this.OpenConnection() == true)
{
//create command and assign the query and connection from the constructor
MySqlCommand cmd = new MySqlCommand(query, connection);
//Execute command
cmd.ExecuteNonQuery();
//close connection
this.CloseConnection();
}
}
//Update statement
public void Update()
{
}
//Delete statement
public void Delete()
{
}
//Select statement
public List<string>[] Select()
{
string query = "SELECT * FROM mytable";
//Create a list to store the result
List<string>[] list = new List<string>[3];
list[0] = new List<string>();
list[1] = new List<string>();
list[2] = new List<string>();
//Open connection
if (this.OpenConnection() == true)
{
//Create Command
MySqlCommand cmd = new MySqlCommand(query, connection);
//Create a data reader and Execute the command
MySqlDataReader dataReader = cmd.ExecuteReader();
//Read the data and store them in the list
if (dataReader.Read())
{
/*list[0].Add(dataReader["username"] + "");
list[1].Add(dataReader["password"] + "");
list[2].Add(dataReader["email"] + "");*/
newscontent.Text = dataReader["username"]; //this is the error
}
//close Data Reader
dataReader.Close();
//close Connection
this.CloseConnection();
//return list to be displayed
return list;
}
else
{
return list;
}
}
//Count statement
//Backup
public void Backup()
{
}
//Restore
public void Restore()
{
}
}
}
}
please help me
,thanks :)

Move all your code from the class DbConnect yo your Form1 class. Then all of your methods have access to your form controls.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using MySql.Data.MySqlClient;
namespace WindowsFormsApplication8
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private MySqlConnection connection;
private string server;
private string database;
private string uid;
private string password;
//Initialize values
private void Initialize()
{
server = "net";
database = "rainbow";
uid = "ok";
password = "passwd!";
string connectionString;
connectionString = "SERVER=" + server + ";" + "DATABASE=" +
database + ";" + "UID=" + uid + ";" + "PASSWORD=" + password + ";";
connection = new MySqlConnection(connectionString);
}
//open connection to database
private bool OpenConnection()
{
try
{
connection.Open();
return true;
}
catch (MySqlException ex)
{
//When handling errors, you can your application's response based
//on the error number.
//The two most common error numbers when connecting are as follows:
//0: Cannot connect to server.
//1045: Invalid user name and/or password.
switch (ex.Number)
{
case 0:
MessageBox.Show("Cannot connect to server. Contact administrator");
break;
case 1045:
MessageBox.Show("Invalid username/password, please try again");
break;
default :
MessageBox.Show("Connected Successfuly!!");
break;
}
return false;
}
}
//Close connection
private bool CloseConnection()
{
try
{
connection.Close();
return true;
}
catch (MySqlException ex)
{
MessageBox.Show(ex.Message);
return false;
}
}
//Insert statement
public void Insert()
{
string query = "INSERT INTO mytable (username, password) VALUES('shryder', 'nopassword')";
//open connection
if (this.OpenConnection() == true)
{
//create command and assign the query and connection from the constructor
MySqlCommand cmd = new MySqlCommand(query, connection);
//Execute command
cmd.ExecuteNonQuery();
//close connection
this.CloseConnection();
}
}
//Update statement
public void Update()
{
}
//Delete statement
public void Delete()
{
}
//Select statement
public List<string>[] Select()
{
string query = "SELECT * FROM mytable";
//Create a list to store the result
List<string>[] list = new List<string>[3];
list[0] = new List<string>();
list[1] = new List<string>();
list[2] = new List<string>();
//Open connection
if (this.OpenConnection() == true)
{
//Create Command
MySqlCommand cmd = new MySqlCommand(query, connection);
//Create a data reader and Execute the command
MySqlDataReader dataReader = cmd.ExecuteReader();
//Read the data and store them in the list
if (dataReader.Read())
{
/*list[0].Add(dataReader["username"] + "");
list[1].Add(dataReader["password"] + "");
list[2].Add(dataReader["email"] + "");*/
newscontent.Text = dataReader["username"]; //this is the error
}
//close Data Reader
dataReader.Close();
//close Connection
this.CloseConnection();
//return list to be displayed
return list;
}
else
{
return list;
}
}
//Count statement
//Backup
public void Backup()
{
}
//Restore
public void Restore()
{
}
}
}
}
Like this your code ahould be able to access the labels, so it should compile. It still doesn't do anything since none of the methods are called.
Edited this on my phone, so couldn't test the code.

Registration allows duplicate user name in Access

I do have a problem in checking username and password in my registration form. When I tend to register the same username and password that's is already in my database(Access), still it allows to register. I just wanna trap it however, I don't know how to that.
What I want to output is that, I want a trap that says "Account Exists, Try Again!" or "Username Exists!"
using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Data.OleDb; using System.Text.RegularExpressions;
namespace Login { public partial class Register : Form {
private OleDbConnection personalConn;
private OleDbCommand oleDbCmd = new OleDbCommand();
private String connParam = #"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=E:\Majel\Tic Tac Toe\Database\data.accdb";
public Register()
{
personalConn = new OleDbConnection(connParam);
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
try
{
personalConn.Open();
oleDbCmd.Connection = personalConn;
if (textBox1.Text != "" && textBox2.Text != "")
{
int temp;
oleDbCmd.CommandText = "INSERT INTO data(Users,Pass) Values('" + this.textBox1.Text.ToString() + "','" + this.textBox2.Text + "');";
temp = oleDbCmd.ExecuteNonQuery();
if (temp > 0)
{
textBox1.Text = null;
textBox2.Text = null;
MessageBox.Show("Registration Success!");
this.Hide();
Form1 frm = new Form1();
frm.Show();
}
personalConn.Close();
}
}
catch (Exception)
{
MessageBox.Show("Invalid!, Duplicate Data.");
}
}
Notes: textBox1= username
textBox2= password Your attention is much highly appreciated. Thank you so much in advance.

Here is code which uses oledbcommand parameters using ? placeholder as mentioned in MSDN Reference. Also I have added using block which should Close opened connection implicitly.
using(OleDbConnection con = new OleDbConnection(connParam))
using(OleDbCommand cmd = new OleDbCommand("select count(*) from data where Users = ?"))
{
con.Open();
cmd.Connection = con;
cmd.Parameters.AddWithValue("#UserName", textBox1.Text);
object objRes = cmd.ExecuteScalar();
if (objRes == null || (int)objRes == 0)
{
cmd.Parameters.Clear();
cmd.CommandText = "INSERT INTO data (Users,Pass) values(?, ?);";
cmd.Parameters.AddWithValue("#Users", textBox1.Text);
cmd.Parameters.AddWithValue("#Pass", textBox2.Text);
int iRes = cmd.ExecuteNonQuery();
if(iRes > 0)
MessageBox.Show("Registration Success!");
}
else
errorProvider2.SetError(textBox1, "This username has been using by another user.");
}

You almost never use data (in this case, a username) as the primary key for a record in a database. Chance are, your access database is set up the same way.
This means that there is nothing at the DBMS layer that will stop this from occurring, short of making the username the primary key (not recommended).
The solution is to perform a SELECT query to get the count of records with that username, and only allow the insert if the count is 0. You might be able to write a trigger to do this for you, and make the DBMS "reject" the insert, but given your (apparent) level with databases, I wouldn't try that at this point.
To get the count:
SELECT Count(*) FROM Users WHERE userName=#userName
A paramaterized query here is crucial to protect against SQL injection.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.OleDb;
using System.Text.RegularExpressions;
namespace Login
{
public partial class Register : Form
{
public Register()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
try
{
if(text1Box1.Text == "" || textBox2.Text == "")
{
MessageBox.Show("Mandatory fields password or user is empty");
retrun; //I'm not sure if this return is need. Remove it if MessageBox "breaks" the execution of the code below.
}
OleDbCommand cmd = new OleDbCommand(#"Select * from Data where User=#User");
cmd.Parameters.AddWithValue("#User", textBox1.Text);
DataSet dst = SqlManager.GetDataSet(cmd, "Data");
if(dst.Tables[0].Rows > 0)
{
MessageBox.Show("User already exist");
return; //again i'm not sure that this return is needed.
}
Insert("Data", "User", textBox1.Text, "Pass", textBox2.Text);
textBox1.Text = null;
textBox2.Text = null;
MessageBox.Show("Registration Success!");
this.Hide();
Form1 frm = new Form1();
frm.Show();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
You need 1 class make it SqlManager.
public class SqlManager
{
private String connectionString = #"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=E:\Majel\Tic Tac Toe\Database\data.accdb";
public static GetOleDbConnection(OleDbCommand cmd)
{
if(cmd.Connection == null)
{
OleDbConnection conn = new OleDbConnection(connectionString);
conn.Open();
cmd.Connection = conn;
return conn;
}
return cmd.Connection;
}
public static int ExecuteNonQuery(SqlCommand cmd)
{
OleDbConnection conn = GetSqlConnection(cmd);
try
{
return cmd.ExecuteNonQuery();
}
catch
{
throw;
}
finally
{
conn.Close();
}
}
public static DataSet GetDataSet(SqlCommand cmd)
{
return GetDataSet(cmd, "Table");
}
public static DataSet GetDataSet(SqlCommand cmd, string defaultTable)
{
OleDbConnection conn = GetSqlConnection(cmd);
try
{
DataSet resultDst = new DataSet();
using (OleDbDataAdapter adapter = new OleDbDataAdapter(cmd))
{
adapter.Fill(resultDst, defaultTable);
}
return resultDst;
}
catch
{
throw;
}
finally
{
conn.Close();
}
}
}
Here is another method you can put in the form class:
public virtual void Insert(string TableName, params object[] colValues)
{
if (colValues == null || colValues.Length % 2 != 0)
throw new ArgumentException("Invalid column values passed in. Expects pairs (ColumnName, ColumnValue).");
OleDbCommand cmd = new OleDbCommand("INSERT INTO " + TableName + " ( {0} ) VALUES ( {1} )");
string insertCols = string.Empty;
string insertParams = string.Empty;
for (int i = 0; i < colValues.Length; i += 2)
{
string separator = ", ";
if (i == colValues.Length - 2)
separator = "";
string param = "#P" + i;
insertCols += colValues[i] + separator;
insertParams += param + separator;
cmd.Parameters.AddWithValue(param, colValues[i + 1]);
}
cmd.CommandText = string.Format(cmd.CommandText, insertCols, insertParams);
DA.SqlManager.ExecuteNonQuery(cmd);
}
Like other guys tell you use parameters in this case you will avoid sql injection. Read in wikipedia about it. Also I add some structure for your program, it is not perfect but I should write a lot for more. It is possible to have some typos here, because I wrote the code here. How you make the check, you fetch the data from database for the user which you write in textbox1.Text. If the dataSet have rows that means at the moment there is existing user with this name. If you don't know what is data set read System.Data.
You should learn to write data access in other classes !

Try this with your Existing Code :
oleDbCmd.CommandText = "INSERT INTO data(Users,Pass) Values('" + this.textBox1.Text.ToString() + "','" + this.textBox2.Text + "') SELECT '" + this.textBox1.Text.ToString() + "','" + this.textBox2.Text + "' WHERE NOT EXISTS(SELECT Users,Pass FROM data WHERE Users='" + this.textBox1.Text.ToString() +"');";
temp = oleDbCmd.ExecuteNonQuery();
if (temp > 0)
{
textBox1.Text = null;
textBox2.Text = null;
MessageBox.Show("Registration Success!");
this.Hide();
Form1 frm = new Form1();
frm.Show();
}
else
{
MessageBox.Show("Username is already Present !!!");
}
It returns 0 if the username is already present in data.

MS Access Oledb column properties

And I solved this problem in VBA using DAO here
Using the Oledb framework, I created a function that can look up a record value. However it only gets the raw value. I need to find the value of the column property called "Row Source"
Can someone explain to me how to find the foreign key value using Oledb
Below is my function for a traditional look up query.
string IDatabase.LookupRecord(string column, string table, string lookupColumn, string lookUpValue)
{
OleDbCommand cmdLookupColumnValue = new OleDbCommand();
string sqlQuery = "SELECT [" + table + "].[" + column + "] " +
"FROM [" + table + "] " +
"WHERE [" + table + "].[" + lookupColumn + "] = '" + lookUpValue + "'";
cmdLookupColumnValue.CommandText = sqlQuery;
cmdLookupColumnValue.CommandType = CommandType.Text;
cmdLookupColumnValue.Connection = connection;
string result = "";
try
{
result = cmdLookupColumnValue.ExecuteScalar().ToString();
}
catch(Exception ex)
{
MessageBox.Show("Query is not valid :" + ex.ToString());
}
return result;
}
EDIT I found the following code here Its the closest Ive gotten so far. It does get column properties like the column Description but it doesnt work for row Source. Any Ideas?
public void Test()
{
string columnName = "Main Space Category";
ADOX.Catalog cat = new ADOX.Catalog();
ADODB.Connection conn = new ADODB.Connection();
conn.Open(connectionString, null, null, 0);
cat.ActiveConnection = conn;
ADOX.Table mhs = cat.Tables["FI - ROOM"];
var columnDescription = mhs.Columns[columnName].Properties["Description"].Value.ToString();
MessageBox.Show(columnDescription);
conn.Close();
}

I strongly suspect that the RowSource property of a table column is so specific to Access that you will have to use DAO to retrieve it. The following C# code is an example of how you might do that:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace daoConsoleApp
{
class Program
{
static void Main(string[] args)
{
string TableName = "Cars";
string FieldName = "CarType";
// This code requires the following COM reference in your project:
//
// Microsoft Office 14.0 Access Database Engine Object Library
//
var dbe = new Microsoft.Office.Interop.Access.Dao.DBEngine();
Microsoft.Office.Interop.Access.Dao.Database db = dbe.OpenDatabase(#"Z:\_xfer\Database1.accdb");
try
{
Microsoft.Office.Interop.Access.Dao.Field fld = db.TableDefs[TableName].Fields[FieldName];
string RowSource = "";
try
{
RowSource = fld.Properties["RowSource"].Value;
}
catch
{
// do nothing - RowSource will remain an empty string
}
if (RowSource.Length == 0)
{
Console.WriteLine("The field is not a lookup field.");
}
else
{
Console.WriteLine(RowSource);
}
}
catch (Exception ex)
{
Console.WriteLine(ex.ToString());
}
}
}
}

SQL Server timeout in recursive code

I have a base class which implements my database connection. I have a second class that inherits this base database class. The second class has some recursion inside of it, where when evaluating it's value, it may instantiate another instance of the second class. The recursion is only a few levels deep. I am running everything single-threaded.
My code will run correctly for about 1 or 2 minutes, then I begin getting consistent errors: "Timeout Expired. The timeout period elapsed prior to obtaining a connection from the pool".
My base class has a destructor which calls the .Dispose() method on the database objects. My second class has a destructor which closes the connection object in the base class.
My connection string to the database specifies a connection timeout = 0.
Any ideas as to why the code will work correctly for a few minutes and then begin timing out trying to connect to the database? I'm baffled.
namespace BaseLib2
{
public class TSBase
{
protected StreamWriter logFile;
protected OleDbCommand queryCmd;
protected OleDbCommand exeCmd;
protected OleDbConnection connection;
protected OleDbDataReader reader;
public SqlConnection sqlconn;//used for BCP
public TSBase()
{
}
~TSBase()
{
try
{
queryCmd.Dispose();
exeCmd.Dispose();
reader.Dispose();
connection.Dispose();
sqlconn.Dispose();
}
catch (Exception ex)
{
Console.WriteLine("BaseLib2 destrutor:" + ex.Message);
}
}
public void ConnectToDB()
{
string connString = "Provider=SQLNCLI11;Server=myserver;Database=mydb;Uid=myid;pwd=password;connection timeout=0";
queryCmd = new OleDbCommand();
exeCmd = new OleDbCommand();
connection = new OleDbConnection(connString);
queryCmd.CommandTimeout = 60000;
exeCmd.CommandTimeout = 60000;
connection.Open();
queryCmd.Connection = connection;
exeCmd.Connection = connection;
string sqlConnString = "server=dc2k8housql;database=mydb;Uid=myid;pwd=password;connection timeout=0";
sqlconn = new SqlConnection(sqlConnString);
sqlconn.Open();
}
public class Expression : BaseLib2.TSBase
{
private string ExpName;
private string ExpressionTxt;
private string sql;
private DateTime Contract_dt;
private DateTime Quote_dt;
private bool SaveToDB;
private string BaseSymbol;
public Expression(string expNameIn, DateTime contract_dtIn, DateTime quote_dtIn)
{
ExpName = expNameIn;
Contract_dt = contract_dtIn;
Quote_dt = quote_dtIn;
try
{
try
{
ConnectToDB();
}
catch (Exception ex)
{
Console.WriteLine("Error in EXP constructor connecting to database." + ex.Message );
throw new Exception("Error in EXP constructor connecting to database.");
}
//get expression text from database
sql = "select expression, save_to_db, coalesce(base_symbol, '') as base_symbol from expressions where exp_name = " + DBI(ExpName);
reader = ReadData(sql);
if (reader.Read())//should only return 1 row
{
ExpressionTxt = reader[0].ToString();
SaveToDB = bool.Parse(reader[1].ToString());
BaseSymbol = reader[2].ToString();
}
reader.Close();
}
catch (Exception ex)
{
Console.WriteLine("Exception in Expression constructor:" + ex.Message);
}
}
~Expression()
{
try
{
connection.Close();
sqlconn.Close();
connection.Dispose();
sqlconn.Dispose();
}
catch (Exception ex)
{
Console.WriteLine("Error in destructor:" + ex.Message);
}
}
public double Eval()
{
try
{
//check to see if there are any $RV in the expression
if (ExpressionTxt.Contains("$RV("))
{
//parse and evaluate the $RV's
String[] split = ExpressionTxt.Split(("$".ToCharArray()));
foreach (string s in split){
Console.WriteLine("s=" + s);
if (s.Length > 3)//make sure we have a string with a symbol in it
{
//for each rv we find, create a new expression and evaluate it
if (s.Substring(0, 3).Contains("RV"))
{
int pStart = s.IndexOf("(");
int pEnd = s.IndexOf(")");
string rvSymb = s.Substring(pStart + 1, pEnd - pStart - 1);
System.Console.WriteLine(rvSymb);
Expression oExp = new Expression(rvSymb, Contract_dt, Quote_dt);
double rVal = oExp.Eval();//recursive call
oExp = null;
ExpressionTxt = ExpressionTxt.Replace("$RV(" + rvSymb + ")", rVal.ToString());
}
}
}
}
//replace SV values in formula
if (ExpressionTxt.Contains("$SV("))
{
//find symbols in $SV brackets and collect contract dates
String[] split = ExpressionTxt.Split (("$".ToCharArray()));
foreach (string s in split)
{
if (s.Length > 3)
{//make sure we have a symbol
if (s.Substring(0, 3).Contains("SV"))
{
int pStart = s.IndexOf("(");
int pEnd = s.IndexOf(")");
string svSymb = s.Substring(pStart + 1, pEnd - pStart - 1);
System.Console.WriteLine("sv=" + svSymb);
//replace $SV with numerical values
double sVal = GetQuoteValue(svSymb);
ExpressionTxt = ExpressionTxt.Replace("$SV(" + svSymb + ")", sVal.ToString());
}
}
}
}
//evaluate
double ret = Evaluate(ExpressionTxt);
Console.WriteLine(ExpName + "=" + ret.ToString());
if (SaveToDB)
{
Console.WriteLine(ExpName + " cd:" + Contract_dt.ToShortDateString() + " qd:" + Quote_dt.ToShortDateString() + ": saving to db...");
sql = "delete from exp_quotes where exp_name = " + DBI(ExpName ) ;
sql = sql + " and contract_dt = " + DBI(Contract_dt.ToShortDateString());
sql = sql + " and quote_dt = " + DBI(Quote_dt.ToShortDateString());
WriteData(sql);
sql = "insert into exp_quotes(exp_name, contract_dt, quote_dt, calculated_dt, price) values(";
sql = sql + DBI(ExpName ) + "," + DBI(Contract_dt.ToShortDateString()) + "," + DBI(Quote_dt.ToShortDateString());
sql = sql + ", getdate(), " + ret + ")";
WriteData(sql);
}
connection.Close();//after we evaluate, close down the connection
connection.Dispose();
return ret;
//return value
}
catch (Exception ex)
{
Console.WriteLine("exp:" + ExpName + " cd:" + Contract_dt.ToShortDateString() + " qd:" + Quote_dt.ToShortDateString() + " = " + ex.Message);
}
return 0;
}
private double GetQuoteValue(string symbIn)
{
double ret = 0;
sql = "select close_val from prices_union_all_vw where symbol = " + DBI(symbIn) + " and contract_dt = " + DBI(Contract_dt.ToShortDateString()) + " and quote_dt = " + DBI(Quote_dt.ToShortDateString());
reader = ReadData(sql);
if (reader.Read())
{
ret = Double.Parse(reader[0].ToString());
reader.Close();
}
else
{//we didn't get a record for the specific quote date, try again using the mostrecent view
sql = "select close_val from prices_union_all_mostrecent_vw where symbol = " + DBI(symbIn) + " and contract_dt = " + DBI(Contract_dt.ToShortDateString());
reader = ReadData(sql);
if (reader.Read())
{
ret = Double.Parse(reader[0].ToString());
}
reader.Close();
}
return ret;
}
private static double Evaluate(string expression)
{
var loDataTable = new DataTable();
var loDataColumn = new DataColumn("Eval", typeof(double), expression);
loDataTable.Columns.Add(loDataColumn);
loDataTable.Rows.Add(0);
return (double)(loDataTable.Rows[0]["Eval"]);
}

You are exhausting your available pool of connections because you are creating a connection to the database for every Expression and sub-Expression that you parse, and they are not being cleaned up in time to be re-used.
Solution: Do not make connections recursively, or iteratively, or whatever. Make one for one purpose and just use it. And if you need to release a connection in-time for you to re-use it, do NOT rely on class destructors, because they do not run when you want them to.
In general, classes that try to allocate limited external resources (like connections) implicitly in their Initializers should be pretty static objects, and you certainly do not normally want to inherit them in a class that is intended to create objects as dynamically as a parser.

Have you tried extending the timeout period?
Add a big timeout to the connection string like "Connect Timeout=1800". This usually helps me when I get such messages.
The other thing you can see is if you can improve the query more.

You might check your Max connection setting for the database. Also check how many active connections are open when new connection attempts start to time out.
How to determine total number of open/active connections in ms sql server 2005