I am trying to doing this:
Read a row from an SQLite db (in GetRuleByID() method)
Update the same row that I just read during (1) (See UpdateStatusForRuleID() method)
However my problem is that SQLite locks the database after the SELECT in GetRuleByID() so that update in UpdateStatusForRuleID() is only successful when called the first time.
I have tried enabling Write-Ahead-Logging in SQLite as well as PRAGMA read_uncommitted=1 in order to avoid SQLite locking the database for the SELECT, but this does not appear to work.
This should be simple but I have so far spent a complete night trying to solve this... Please help !
private static MicroRuleEngine.Rule GetRuleByID(int ruleID, SQLiteConnection connection, out Dictionary<string, string> dict)
{
dict = new Dictionary<string, string>();
string sql = String.Format("select * from rules WHERE ID = {0} ", ruleID.ToString());
SQLiteCommand command = new SQLiteCommand(sql, connection);
SQLiteDataReader reader = command.ExecuteReader();
if (reader.HasRows)
{
reader.Read();
// Convert row into a dictionary
for (int lp = 0; lp < reader.FieldCount; lp++)
{
dict.Add(reader.GetName(lp), reader.GetValue(lp) as string);
}
string json = dict["fulljson"];
MicroRuleEngine.Rule r = Newtonsoft.Json.JsonConvert.DeserializeObject<MicroRuleEngine.Rule>(json);
//command.Dispose();
return r;
}
}
internal static void UpdateStatusForRuleID(SQLConnectionManager DBMANAGER, int ruleID, bool status)
{
Dictionary<string, string> dict = null;
string dbVal = (status) ? "1" : "0";
MicroRuleEngine.Rule r = null;
string newJSON = null;
using (SQLiteConnection connection = DBMANAGER.CreateConnection())
{
r = GetRuleByID(ruleID, connection, out dict);
r.Active = (status);
newJSON = Newtonsoft.Json.JsonConvert.SerializeObject(r);
Thread.Sleep(1000);
string sql = "UPDATE rules SET active = #a, fulljson=#j WHERE ID = #i";
using (var command = new SQLiteCommand(sql, connection))
{
command.Parameters.Add(new SQLiteParameter("#a", dbVal));
command.Parameters.Add(new SQLiteParameter("#i", ruleID));
command.Parameters.Add(new SQLiteParameter("#j", newJSON));
command.ExecuteNonQuery(); // Database is locked here ???
}
connection.Close();
}
}
"Database is locked" means that some other connection (in the same or some other process) still has an active transaction.
You don't need multiple connections (unless you are using multiple threads); just use a single connection object for all database accesses.
Ensure that all command, reader, and transaction objects (and connections, if you decide to use temporary ones) are properly cleaned up, by using using:
using (var command = new SQLiteCommand(sql, connection))
using (var reader = command.ExecuteReader())
{
if (reader.HasRows)
...
}
Apparently, the code below works. I basically dropped the GetRuleByID() method (but then I had to re-write 4 other methods)
Thanks to all who provided input.
internal static void UpdateStatusForRuleID(SQLConnectionManager DBMANAGER, int ruleID, bool status)
{
string dbVal = (status) ? "1" : "0";
MicroRuleEngine.Rule r = null;
string newJSON = null;
using (SQLiteConnection conn = DBMANAGER.CreateConnection())
{
string sql = String.Format("select * from rules WHERE ID = {0} ", ruleID.ToString());
using (var command = new SQLiteCommand(sql, conn))
using (var reader = command.ExecuteReader())
{
if (reader.HasRows)
{
reader.Read();
string json = reader["fulljson"].ToString();
r = Newtonsoft.Json.JsonConvert.DeserializeObject<MicroRuleEngine.Rule>(json);
r.Active = (status);
newJSON = Newtonsoft.Json.JsonConvert.SerializeObject(r);
string sql2 = "UPDATE rules SET active = #a, fulljson=#j WHERE ID = #i";
using (var command2 = new SQLiteCommand(sql2, conn))
{
command2.Parameters.Add(new SQLiteParameter("#a", dbVal));
command2.Parameters.Add(new SQLiteParameter("#i", ruleID));
command2.Parameters.Add(new SQLiteParameter("#j", newJSON));
command2.ExecuteNonQuery();
}
}
}
}
}
Related
I have the following code which establishing an SQL connection inside of a project I am working on. What I want to do is to create a for loop which contains a method and every time the loop repeats the method runs with a different value until all views of the returned query are used.
I can't figure out how to refer to every value of the view without saving the view to a list or an array first. Any ideas?
SqlConnection Con = new SqlConnection(#"Data Source=localhost\**;Initial Catalog=ML;User Id=sa;Password='**'");
string sql = #"select product_id,Name from E_PRODUCT_PROPERTY";
var mylist = new List<WineRating>();
using (var command = new SqlCommand(sql, Con))
{
Con.Open();
using (var reader = command.ExecuteReader())
{
while (reader.Read())
new WineRating { product_id = reader.GetInt32(0), Name = reader.GetString(1) };
///Here goes the code I suppose
method_name(reader.GetInt32(0), reader.GetString(1));
}
}
public static int method_name(int product_id, string Name)
{
int num = x *2;
Console.WriteLine(num + Name);
}
Perhaps like this:
using (var reader = command.ExecuteReader())
{
while (reader.Read())
{
MyMethodToPrintToScreen(reader.GetInt32(0), reader.GetString(1));
}
}
With the method to print to screen
private static void MyMethodToPrintToScreen(int id, string product)
{
//Do whatever you wish with the data: example
Console.WriteLine($"My id: {id} | Product: {product}");
}
Edit
Let me make it even more obvious(using your exact code):
SqlConnection Con = new SqlConnection(#"Data Source=localhost\**;Initial Catalog=ML;User Id=sa;Password='**'");
string sql = #"select product_id,Name from E_PRODUCT_PROPERTY";
var mylist = new List<WineRating>();
using (var command = new SqlCommand(sql, Con))
{
Con.Open();
using (var reader = command.ExecuteReader())
{
while (reader.Read())
{
method_name(reader.GetInt32(0), reader.GetString(1));
}
}
}
I have put together the following method:
public static ArrayList DbQueryToArry()
{
string SqlCString = "connString";
SqlConnection connection = null;
ArrayList valuesList = new ArrayList();
connection = new SqlConnection(SqlCString);
connection.Open();
SqlCommand command = new SqlCommand("Select CLIENTNO, ACCOUNT_Purpose from audit.ACCOUNTS_AUDIT", connection);
SqlDataReader reader = command.ExecuteReader();
while (reader.Read())
{
valuesList.Add(Convert.ToString(reader[0]));
}
return valuesList;
}
I'd like to be able to run an assertion like this one:
var a = DbQueryToArry();
Assert.IsTrue(a.Contains("some value"));
Given reader [0]
valuesList.Add(Convert.ToString(reader[0]));
I only get the first column (CLIENTINFO) into the array and not the second (ACCOUNT_Purpose). How should I modify the code to get both ?
In addition, the returned values could be either a String or Int so would my current code version should be handling both ?
Thanks in advance.
If we switch from obsolete ArrayList to something like IEnumerable<T>:
public static IEnumerable<IDataRecord> DbQueryToArray(string sql) {
if (null == sql)
throw new ArgumentNullException(nameof(sql));
//TODO: do not hardcode connetcion string but read it (say, from Settings)
string SqlCString = "connString";
//DONE: Wrap IDisposable into using
using (SqlConnection connection = new SqlConnection(SqlCString)) {
connection.Open();
//DONE: Wrap IDisposable into using
using (SqlCommand command = new SqlCommand(sql, connection)) {
//DONE: Wrap IDisposable into using
using (SqlDataReader reader = command.ExecuteReader()) {
while (reader.Read()) {
yield return reader as IDataRecord;
}
}
}
}
}
then you can use Linq in order to query the result:
var a = DbQueryToArray("Select CLIENTNO, ACCOUNT_Purpose from audit.ACCOUNTS_AUDIT");
Assert.IsTrue(a.Any(record =>
Convert.ToString(record["CLIENTNO"]) == "some value"));
Assert.IsTrue(a.Any(record =>
Convert.ToString(record["ACCOUNT_Purpose"]) == "some other value"));
If you don't want execute query several times, you can materialize the results:
var a = DbQueryToArray("Select CLIENTNO, ACCOUNT_Purpose from audit.ACCOUNTS_AUDIT")
.ToList();
Assert.IsTrue(a.Any(record => Convert.ToString(record[0]) == "some value"));
Assert.IsTrue(a.Any(record => Convert.ToString(record[1]) == "some other value"));
Finally (see comments below), if we want to test if any field in any record has the value:
var a = DbQueryToArray("Select CLIENTNO, ACCOUNT_Purpose from audit.ACCOUNTS_AUDIT")
.SelectMany(line => {
// Flatten the cursor into IEnumerable<String>
string[] result = new string[line.FieldCount];
for (int i = 0; i < result.Length; ++i)
result[i] = Convert.ToString(line[i]);
return result;
});
a.Any(item => item == "some value");
It is because you only read the first value of the reader. Reader.Read() read each row one by one and Convert.ToString(reader[0])) means that you want to read the first column as string.
That's cause you are getting only the first column. You can do something like below by specifying the column name
while (reader.Read())
{
valuesList.Add(Convert.ToString(reader["CLIENTNO"]));
valuesList.Add(Convert.ToString(reader["ACCOUNT_Purpose"]));
}
Moreover, since you are converting all the columns to string; I would suggest to use a strongly typed collection like List<string> rather then ArrayList valuesList = new ArrayList();
The other answers are good, However some concerns
Lets stop using ArrayList, and use a List<T> instead
Lets use a using statement where you can
Note : I have used a ValueTuple to return more than 1 field
Example
public static List<(string clientNo, string account)> DbQueryToArray()
{
const string SqlCString = "connString";
var valuesList = new List<(string clientNo, string account)>();
using (var connection = new SqlConnection(SqlCString))
{
connection.Open();
using (var command = new SqlCommand("Select CLIENTNO, ACCOUNT_Purpose from audit.ACCOUNTS_AUDIT", connection))
{
var reader = command.ExecuteReader();
while (reader.Read())
valuesList.Add(((string)reader[0],(string)reader[1]) );
}
}
return valuesList;
}
Usage
var results = DbQueryToArray();
Assert.IsTrue(results.Any(x => x.clientNo == someValue || x.account == someValue));
best practice is to check first if the reader has rows
reader.HasRows
then close the reader and the connection
your code should look like this:
public static ArrayList DbQueryToArry()
{
string SqlCString = "connString";
SqlConnection connection = null;
ArrayList valuesList = new ArrayList();
connection = new SqlConnection(SqlCString);
using (connection)
{
connection.Open();
SqlCommand command = new SqlCommand("Select CLIENTNO, ACCOUNT_Purpose from audit.ACCOUNTS_AUDIT", connection);
SqlDataReader reader = command.ExecuteReader();
if (reader.HasRows)
{
while (reader.Read())
{
valuesList.Add(Convert.ToString(reader[0]));
valuesList.Add(Convert.ToString(reader[1])); // add to valuelist
}
}
reader.Close(); // close reader
} //dispose connection
return valuesList;
}
Use DataTable and SqlDataAdapter to get query result in form of table. Something like this:
string connString = #"your connection string here";
string query = "select * from table";
DataTable dataTable = new DataTable();
SqlConnection conn = new SqlConnection(connString);
SqlCommand cmd = new SqlCommand(query, conn);
conn.Open();
// create data adapter
SqlDataAdapter da = new SqlDataAdapter(cmd);
// this will query your database and return the result to your datatable
da.Fill(dataTable);
conn.Close();
da.Dispose();
Then you can use dataTable object to see if particular values exist.
Why only the else condition runs? Postalcode column is float, City column is nvarchar. I think the fail is the string may be mistake.
private void txt_st_postalcode_Leave(object sender, EventArgs e)
{
using (var connection = new SqlConnection("Data Source=mypublicip\\SQLEXPRESS2017;Initial Catalog=studentreg; User = myusername; Password=mypassword;"))
{
connection.Open();
using (var command = new SqlCommand("SELECT City FROM Cities WHERE Postcode=#Postcode", connection))
{
command.Parameters.AddWithValue("#Postcode", "10101");
using (var reader = command.ExecuteReader())
{
string txt_st_postalcode = reader.Read() ?
reader[1] as string : ("City");
if (reader.Read())
{
txt_st_city.Text = reader.GetString(reader.GetOrdinal("City"));
}
else
{
MessageBox.Show("Sh*t!");
}
}
}
}
}
Not too sure how these postcodes work (different in the UK), but given that you're using ExecuteReader you appear to be expecting multiple results. As the comments have pointed out, you're currently reading the results twice; however, you should probably have some form of loop; for example:
using (var command = new SqlCommand("SELECT City FROM Cities WHERE Postcode=#Postcode", connection))
{
command.Parameters.AddWithValue("#Postcode", "10101");
using (var reader = command.ExecuteReader())
{
while (reader.Read())
{
string txt_st_postalcode = reader[0] as string;
//txt_st_city.Text = reader.GetString(reader.GetOrdinal("City"));
// Depends what you're doing here?
}
}
}
If you only expect a single result, try using ExecuteScalar() which will return a single result; for example:
using (var command = new SqlCommand("SELECT City FROM Cities WHERE Postcode=#Postcode", connection))
{
command.Parameters.AddWithValue("#Postcode", "10101");
txt_st_city.Text = command.ExecuteScalar();
}
Firstly, if you need to read PostCode from the reader, you have to select first. So, change your query.
using (var command = new SqlCommand("SELECT City, PostCode FROM Cities WHERE Postcode=#Postcode", connection))
Secondly, calling read once per row before getting data.
if (reader.Read())
{
txt_st_postalcode .Text = reader.GetString(reader.GetOrdinal("PostCode"));
txt_st_city.Text = reader.GetString(reader.GetOrdinal("City"));
}
else
{
MessageBox.Show("Sh*t!");
}
I am trying to return data using IEnumerable with given fields, where I am calling the the method I want to reference the data with given field name and return that.
Example, here is the function
public IEnumerable<IDataRecord> GetSomeData(string fields, string table, string where = null, int count = 0)
{
string sql = "SELECT #Fields FROM #Table WHERE #Where";
using (SqlConnection cn = new SqlConnection(db.getDBstring(Globals.booDebug)))
using (SqlCommand cmd = new SqlCommand(sql, cn))
{
cmd.Parameters.Add("#Fields", SqlDbType.NVarChar, 255).Value = where;
cn.Open();
using (IDataReader rdr = cmd.ExecuteReader())
{
while (rdr.Read())
{
yield return (IDataRecord)rdr;
}
}
}
}
Calling:
IEnumerable<IDataRecord> data = bw.GetSomeData("StaffCode, Perms", "BW_Staff", "StaffCode = 'KAA'");
What must I do to return the data this way or what way ?
string staffCode = data["StaffCode"].ToString();
string perms = data["Perms"].ToString();
Thanks for any help
your data variable is a collection of rows. You need to iterate over the collection to do something interesting with each row.
foreach (var row in data)
{
string staffCode = row["StaffCode"].ToString();
string perms = row["Perms"].ToString();
}
Update:
Based on your comment that you only expect GetSomeData(...) to return a single row, I'd suggest 1 of two things.
Change the signature of GetSomeData to return an IDataRecord. and remove "yield" from the implementation.
public IDataRecord GetSomeData(string fields, string table, string where = null, int count = 0)
{
string sql = "SELECT #Fields FROM #Table WHERE #Where";
using (SqlConnection cn = new SqlConnection(db.getDBstring(Globals.booDebug)))
using (SqlCommand cmd = new SqlCommand(sql, cn))
{
cmd.Parameters.Add("#Fields", SqlDbType.NVarChar, 255).Value = where;
cn.Open();
using (IDataReader rdr = cmd.ExecuteReader())
{
while (rdr.Read())
{
return (IDataRecord)rdr;
}
}
}
}
}
Or
var row = data.FirstOrDefault();
if (row != null)
{
string staffCode = row["StaffCode"].ToString();
string perms = row["Perms"].ToString();
}
Remarks:
Your implementation of GetSomeData is incomplete. You are not even using several of the parameters, most importantly the fields parameter. And conceptually in SQL you can't parameterize which fields get returned or which table gets used (etc.), but rather you need to construct a dynamic query and execute it.
Update 2
Here is an implementation of GetSomeData that constructs a proper query (in C# 6, let me know if you need it in an earlier version).
public IEnumerable<IDataRecord> GetSomeData(IEnumerable<string> fields, string table, string where = null, int count = 0)
{
var predicate = string.IsNullOrWhiteSpace(where) ? "" : " WHERE " + where;
string sql = $"SELECT { string.Join(",", fields) } FROM {table} {predicate}";
using (SqlConnection cn = new SqlConnection(db.getDBstring(Globals.booDebug)))
using (SqlCommand cmd = new SqlCommand(sql, cn))
{
cn.Open();
using (IDataReader rdr = cmd.ExecuteReader())
{
while (rdr.Read())
{
yield return (IDataRecord)rdr;
}
}
}
}
And here is how you would use it.
IEnumerable<IDataRecord> data = bw.GetSomeData(new[] { "StaffCode", "Perms" }, "BW_Staff", "StaffCode = 'KAA'");
You can either enumerate it or call .FirstOrDefault, it's your choice. Each time you call GetSomeData, it will run the query.
Update 3
GetSomeData implemented with earlier versions of C#
public IEnumerable<IDataRecord> GetSomeData(IEnumerable<string> fields, string table, string where = null, int count = 0)
{
var predicate = string.IsNullOrEmpty(where) ? "" : " WHERE " + where;
string sql = string.Format("SELECT {0} FROM {1} {2}", string.Join(",", fields), table, predicate);
using (SqlConnection cn = new SqlConnection(db.getDBstring(Globals.booDebug)))
using (SqlCommand cmd = new SqlCommand(sql, cn))
{
cn.Open();
using (IDataReader rdr = cmd.ExecuteReader())
{
while (rdr.Read())
{
yield return (IDataRecord)rdr;
}
}
}
}
I have the following code which should be able to get the primary key in a table
public List<string> GetPrimaryKeysForTable(string tableName)
{
List<String> retVal = new List<string>();
SqlCommand command = connector.GetCommand("sp_pkeys");
command.CommandType = System.Data.CommandType.StoredProcedure;
command.Parameters.AddWithValue("#table_name", typeof(SqlChars)).Value = tableName;
SqlDataReader reader = command.ExecuteReader();
while (reader.Read())
{
retVal.Add(reader[3].ToString());
}
return retVal;
}
I have a table called Users in my database. When I pass Users in as my parameter, the reader returns no results. Any idea why this might be failing to return my primary keys?
Try this instead:
command.Parameters.Add("#table_name", SqlDbType.NVarChar).Value = tableName;
It looks like you have an issue with your usage of .AddWithValue() which may be causing your problem. See the fix below:
public List<string> GetPrimaryKeysForTable(string tableName)
{
List<string> retVal = new List<string>();
SqlCommand command = connector.GetCommand("sp_pkeys");
command.CommandType = System.Data.CommandType.StoredProcedure;
command.Parameters.AddWithValue("#table_name", tableName);
SqlDataReader reader = command.ExecuteReader();
while (reader.Read())
{
retVal.Add(reader[3].ToString());
}
return retVal;
}
In your example you are attempting to add the #table_name as a Type rather than a string.
Any chance it needs to be qualified with the schema? Something like:
command.Parameters.AddWithValue("#table_name", typeof(SqlChars)).Value = "dbo." + tableName;
or:
command.Parameters.AddWithValue("#schema", "dbo");
Or is there some parm you need to add to tell it the database inside the server?
You can simply use as below, would you please try it out:
command.Parameters.AddWithValue("#table_name", ("dbo." + tableName));
The stored procedure 'sp_pkeys' takes three parameters:
command.Parameters.Add("#table_name", SqlDbType.NVarChar).Value = tableName;
command.Parameters.Add("#table_owner", SqlDbType.NVarChar).Value = tableOwner;
command.Parameters.Add("#table_qualifier", SqlDbType.NVarChar).Value = tableQualifier;
It works with just #table_name but could try passing all three to see if it makes a difference.
Question: Does your table have any keys defined?
I have run the slightly modified code below against severa tables in a test DB of my own and it works as expected:
static class Program
{
static void Main(string[] args)
{
var connStr = new SqlConnectionStringBuilder
{
DataSource = "localhost",
InitialCatalog = "RichTest",
IntegratedSecurity = true
};
using (var conn = new SqlConnection(connStr.ToString()))
{
conn.Open();
var parents = GetPrimaryKeysForTable(conn, "People");
Console.WriteLine("Parent Keys:");
foreach (var p in parents)
{
Console.WriteLine(" {0}", p);
}
}
}
static IList<string> GetPrimaryKeysForTable(SqlConnection conn, string tableName)
{
if (conn == null) throw new ArgumentNullException("Value is null", "conn");
if (string.IsNullOrWhiteSpace(tableName)) throw new ArgumentNullException("Value is null or emtpy", "tableName");
List<String> retVal = new List<string>();
using (var command = new SqlCommand
{
Connection = conn,
CommandText = "sp_pkeys",
CommandType = CommandType.StoredProcedure
})
{
command.Parameters.AddWithValue("#table_name", typeof(SqlChars)).Value = tableName;
SqlDataReader reader = command.ExecuteReader();
while (reader.Read())
{
retVal.Add(reader["COLUMN_NAME"].ToString());
}
}
return retVal;
}
}