I am using NpgSQL with PostgreSQL and ADO.NET. Forgive the simplicity of the question as I just started using PostgreSQL and NpgSQL this week.
Something like this works fine:
[Test]
public void InsertNoParameters()
{
NpgsqlConnection conn = new NpgsqlConnection("Host=localhost; Database=postgres; User ID=postgres; Password=password");
conn.Open();
IDbCommand command = conn.CreateCommand();
string sql = "INSERT INTO Customers (FirstName,LastName) VALUES ('Test','Tube')";
command.CommandText = sql;
command.ExecuteNonQuery();
conn.Close();
}
When I put in parameters I get the error message:
Npgsql.NpgsqlException : ERROR: 42703: column "_firstname" does not exist
[Test]
public void InsertWithParameters()
{
NpgsqlConnection conn = new NpgsqlConnection("Host=localhost; Database=postgres; User ID=postgres; Password=password");
conn.Open();
IDbCommand command = conn.CreateCommand();
string sql = "INSERT INTO Customers (FirstName,LastName) VALUES (_FirstName,_LastName)";
command.CommandText = sql;
var parameter = command.CreateParameter();
parameter.ParameterName = "_FirstName";
parameter.Value = "Test";
command.Parameters.Add(parameter);
parameter = command.CreateParameter();
parameter.ParameterName = "_LastName";
parameter.Value = "Tube";
command.Parameters.Add(parameter);
command.ExecuteNonQuery();
conn.Close();
}
The responses in the comments are correct:
Npgsql doesn't support _ as a parameter placeholder notation. You should be using # or : (so #FirstName or :FirstName, not _FirstName).
PostgreSQL will automatically lower-case your table and column names unless they are double-quoted. Either use lower-case names for everything (simpler) or quote identifiers in your SQL queries.
So your code should look more or less like this:
IDbCommand command = conn.CreateCommand();
string sql = "INSERT INTO Customers (first_name, last_name) VALUES (#FirstName,#LastName)";
command.CommandText = sql;
var parameter = command.CreateParameter();
parameter.ParameterName = "FirstName";
parameter.Value = "Test";
command.Parameters.Add(parameter);
I cant get reliable checking for database existence in NET/Npgsql at my program startup.
Here is code:
Public Function dbExists(ByVal _dbName As String) As Boolean
Dim retval As Boolean = False
Using mCon As New NpgsqlConnection(String.Format( _
"Server={0};Port={1};User Id={2};Password={3};", _
dbserver, dbport, "postgres", dbpass))
Try
mCon.Open()
Using nCom = New NpgsqlCommand("SELECT 1 FROM pg_database WHERE datname='" + _dbName + "'", mCon)
retval = CBool(nCom.ExecuteScalar())
End Using
Catch ex As Exception
retval = False
End Try
End Using
Return retval
End Function
This function return True no matter database exists or not.
I also try with null checking on ExecuteScalar, getting Count(*) and all what I can without better result.
What to do to get it working?
Null checking on 'ExecuteScalar()' works for me (PostgreSQL 9.3 and Npgsql 2.0.12).
Are you checking 'ExecuteScalar() == null'?
ExecuteScalar will return a .NET null not DBNull.Value (since it is not a record with a null value, it signifies no matching result).
I'm not a VB person but here's how I achieved it in C#:
bool dbExists;
using (NpgsqlConnection conn = new NpgsqlConnection("Server=127.0.0.1;Port=5432;Database=postgres;User Id=postgres;Password=testpass"))
{
conn.Open();
string cmdText = "SELECT 1 FROM pg_database WHERE datname='temp'";
using (NpgsqlCommand cmd = new NpgsqlCommand(cmdText, conn))
{
dbExists = cmd.ExecuteScalar() != null;
}
}
Is there any way to log all requests ongoing to a database or can you only log snapshots to a database?
The following example relies upon OLEDB 4.0 which is not available for 64bit processes. You can either select another data provider (e.g. SQLServer) or you can force Fiddler to run in 32bit mode.
Add the following to the Rules file to create a new menu item.
// Log the currently selected sessions in the list to a database.
// Note: The DB must already exist and you must have permissions to write to it.
public static ToolsAction("Log Selected Sessions")
function DoLogSessions(oSessions: Fiddler.Session[]){
if (null == oSessions || oSessions.Length < 1){
MessageBox.Show("Please select some sessions first!");
return;
}
var strMDB = "C:\\log.mdb";
var cnn = null;
var sdr = null;
var cmd = null;
try
{
cnn = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + strMDB);
cnn.Open();
cmd = new OleDbCommand();
cmd.Connection = cnn;
for (var x = 0; x < oSessions.Length; x++){
var strSQL = "INSERT into tblSessions ([ResponseCode],[URL]) Values (" +
oSessions[x].responseCode + ", '" + oSessions[x].url + "')";
cmd.CommandText = strSQL;
cmd.ExecuteNonQuery();
}
}
catch (ex){
MessageBox.Show(ex);
}
finally
{
if (cnn != null ){
cnn.Close();
}
}
}
Note: To use the Database Objects in Fiddler 2.3.9 and below, you'll need to add system.data to the References list inside Tools | Fiddler Options | Extensions | Scripting. In 2.3.9.1 and later, this reference will occur automatically.
Then, list the new import at the top of your rules script:
import System.Data.OleDb;
see FiddlerScript CookBook
I am working with a system that has many stored procedures that need to be displayed. Creating entities for each of my objects is not practical.
Is it possible and how would I return a DataTable using ExecuteStoreQuery ?
public ObjectResult<DataTable> MethodName(string fileSetName) {
using (var dataContext = new DataContext(_connectionString))
{
var returnDataTable = ((IObjectContextAdapter)dataContext).ObjectContext.ExecuteStoreQuery<DataTable>("SP_NAME","SP_PARAM");
return returnDataTable;
}
Yes it's possible, but it should be used for just dynamic result-set or raw SQL.
public DataTable ExecuteStoreQuery(string commandText, params Object[] parameters)
{
DataTable retVal = new DataTable();
retVal = context.ExecuteStoreQuery<DataTable>(commandText, parameters).FirstOrDefault();
return retVal;
}
Edit: It's better to use classical ADO.NET to get the data model rather than using Entity Framework because most probably you cannot use DataTable even if you can run the method: context.ExecuteStoreQuery<DataTable>(commandText, parameters).FirstOrDefault();
ADO.NET Example:
public DataSet GetResultReport(int questionId)
{
DataSet retVal = new DataSet();
EntityConnection entityConn = (EntityConnection)context.Connection;
SqlConnection sqlConn = (SqlConnection)entityConn.StoreConnection;
SqlCommand cmdReport = new SqlCommand([YourSpName], sqlConn);
SqlDataAdapter daReport = new SqlDataAdapter(cmdReport);
using (cmdReport)
{
SqlParameter questionIdPrm = new SqlParameter("QuestionId", questionId);
cmdReport.CommandType = CommandType.StoredProcedure;
cmdReport.Parameters.Add(questionIdPrm);
daReport.Fill(retVal);
}
return retVal;
}
No, I don't think that'll work - Entity Framework is geared towards returning entities and isn't meant to return DataTable objects.
If you need DataTable objects, use straight ADO.NET instead.
This method uses the connection string from the entity framework to establish an ADO.NET connection, to a MySQL database in this example.
using MySql.Data.MySqlClient;
public DataSet GetReportSummary( int RecordID )
{
var context = new catalogEntities();
DataSet ds = new DataSet();
using ( MySqlConnection connection = new MySqlConnection( context.Database.Connection.ConnectionString ) )
{
using ( MySqlCommand cmd = new MySqlCommand( "ReportSummary", connection ) )
{
MySqlDataAdapter adapter = new MySqlDataAdapter( cmd );
adapter.SelectCommand.CommandType = CommandType.StoredProcedure;
adapter.SelectCommand.Parameters.Add( new MySqlParameter( "#ID", RecordID ) );
adapter.Fill( ds );
}
}
return ds;
}
Yes it can easily be done like this:
var table = new DataTable();
using (var ctx = new SomeContext())
{
var cmd = ctx.Database.Connection.CreateCommand();
cmd.CommandText = "Select Col1, Col2 from SomeTable";
cmd.Connection.Open();
table.Load(cmd.ExecuteReader());
}
By the rule, you shouldn't use a DataSet inside a EF application. But, if you really need to (for instance, to feed a report), that solution should work (it's EF 6 code):
DataSet GetDataSet(string sql, CommandType commandType, Dictionary<string, Object> parameters)
{
// creates resulting dataset
var result = new DataSet();
// creates a data access context (DbContext descendant)
using (var context = new MyDbContext())
{
// creates a Command
var cmd = context.Database.Connection.CreateCommand();
cmd.CommandType = commandType;
cmd.CommandText = sql;
// adds all parameters
foreach (var pr in parameters)
{
var p = cmd.CreateParameter();
p.ParameterName = pr.Key;
p.Value = pr.Value;
cmd.Parameters.Add(p);
}
try
{
// executes
context.Database.Connection.Open();
var reader = cmd.ExecuteReader();
// loop through all resultsets (considering that it's possible to have more than one)
do
{
// loads the DataTable (schema will be fetch automatically)
var tb = new DataTable();
tb.Load(reader);
result.Tables.Add(tb);
} while (!reader.IsClosed);
}
finally
{
// closes the connection
context.Database.Connection.Close();
}
}
// returns the DataSet
return result;
}
In my Entity Framework based solution I need to replace one of my Linq queries with sql - for efficiency reasons.
Also I want my results in a DataTable from one stored procedure so that I could create a table value parameter to pass into a second stored procedure. So:
I'm using sql
I don't want a DataSet
Iterating an IEnumerable probably isn't going to cut it - for efficiency reasons
Also, I am using EF6, so I would prefer DbContext.SqlQuery over ObjectContext.ExecuteStoreQuery as the original poster requested.
However, I found that this just didn't work:
_Context.Database.SqlQuery<DataTable>(sql, parameters).FirstOrDefault();
This is my solution. It returns a DataTable that is fetched using an ADO.NET SqlDataReader - which I believe is faster than a SqlDataAdapter on read-only data. It doesn't strictly answer the question because it uses ADO.Net, but it shows how to do that after getting a hold of the connection from the DbContext
protected DataTable GetDataTable(string sql, params object[] parameters)
{
//didn't work - table had no columns or rows
//return Context.Database.SqlQuery<DataTable>(sql, parameters).FirstOrDefault();
DataTable result = new DataTable();
SqlConnection conn = Context.Database.Connection as SqlConnection;
if(conn == null)
{
throw new InvalidCastException("SqlConnection is invalid for this database");
}
using (SqlCommand cmd = new SqlCommand(sql, conn))
{
cmd.Parameters.AddRange(parameters);
conn.Open();
using (SqlDataReader reader = cmd.ExecuteReader())
{
result.Load(reader);
}
return result;
}
}
The easiest way to return a DataTable using the EntityFramework is to do the following:
MetaTable metaTable = Global.DefaultModel.GetTable("Your EntitySetName");
For example:
MetaTable metaTable = Global.DefaultModel.GetTable("Employees");
Maybe your stored procedure could return a complex type?
http://blogs.msdn.com/b/somasegar/archive/2010/01/11/entity-framework-in-net-4.aspx
I need to learn ADO.NET to build applications based on MS Office. I have read a good deal about ADO.NET in the MSDN Library, but everything seems rather messy to me.
What are the basics one must figure out when using ADO.NET? I think a few key words will suffice to let me organize my learning.
There are three key components (assuming ur using SQL server):
SQLConnection
SqlCommand
SqlDataReader
(if you're using something else, replace Sql with "Something", like MySqlConnection, OracleCommand)
Everything else is just built on top of that.
Example 1:
using (SqlConnection connection = new SqlConnection("CONNECTION STRING"))
using (SqlCommand command = new SqlCommand())
{
command.commandText = "SELECT Name FROM Users WHERE Status = #OnlineStatus";
command.Connection = connection;
command.Parameters.Add("#OnlineStatus", SqlDbType.Int).Value = 1; //replace with enum
connection.Open();
using (SqlDataReader dr = command.ExecuteReader))
{
List<string> onlineUsers = new List<string>();
while (dr.Read())
{
onlineUsers.Add(dr.GetString(0));
}
}
}
Example 2:
using (SqlConnection connection = new SqlConnection("CONNECTION STRING"))
using (SqlCommand command = new SqlCommand())
{
command.commandText = "DELETE FROM Users where Email = #Email";
command.Connection = connection;
command.Parameters.Add("#Email", SqlDbType.VarChar, 100).Value = "user#host.com";
connection.Open();
command.ExecuteNonQuery();
}
Another way of getting a command object is to call connection.CreateCommand().
That way you shouldn't have to set the Connection property on the command object.