I was trying to create shortest possible code to execute "non query" commands. Is it possible somehow to instruct to implicitly open the connection without using conn.Open()
public static int ExecuteNonSelect(string nonSelect)
{
string conString = #"Data Source=...";
int affected;
using (SqlConnection conn = new SqlConnection(conString))
{
using (SqlCommand cmd = new SqlCommand(nonSelect, conn))
{
conn.Open();
affected = cmd.ExecuteNonQuery();
conn.Close();
}
}
return affected;
}
In case of the SqlDataAdapter() class this was not needed:
public static DataTable ExecuteSelect(string selectQuery)
{
string constring = #"Data Source=...";
DataTable dt = new DataTable();
using (SqlConnection conn = new SqlConnection(constring))
{
using (SqlDataAdapter da = new SqlDataAdapter(selectQuery, conn))
{
da.Fill(dt); // calls ExecuteReader internally
}
}
return dt;
}
Related
I'm trying to fill a datagridview with SQL Server table data and I get an error:
ExecuteReader: Connection property has not been initialized.
How do I fix this ?
private void BlackListLoad()
{
DataTable dt = new DataTable();
SqlCommand cmd = new SqlCommand();
BindingSource bs = new BindingSource();
var table = dt;
var connection =
#"Data Source=someone-someone\SQLEXPRESS;Initial Catalog=test;Integrated Security=True;Connect Timeout=30;Encrypt=False;TrustServerCertificate=True;ApplicationIntent=ReadWrite;MultiSubnetFailover=False";
using (var con = new SqlConnection { ConnectionString = connection })
{
if (con.State == ConnectionState.Closed)
{
con.Open();
}
try
{
cmd.CommandText = #"SELECT * FROM [dbo].[Blacklist1]";
table.Load(cmd.ExecuteReader());
bs.DataSource = table;
ListGrid.ReadOnly = true;
ListGrid.DataSource = bs;
}
catch (SqlException ex)
{
MessageBox.Show(ex.Message + " sql query error.");
}
}
}
You haven't given your SqlCommand a connection! As it states you need to do this. You can fix this by doing:
cmd.Connection = con; just before you execute the reader.
Read here for more information: https://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.connection(v=vs.110).aspx
It also looks like you're not opening your connection, which can be fixed with:
con.Open();
With a new connection object, you do not need to check whether it's open, because it won't be.
Try it this way.
using System;
using System.Data;
using System.Windows.Forms;
using System.Data.SqlClient;
namespace WindowsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
string connectionString = "Data Source=.;Initial Catalog=pubs;Integrated Security=True";
string sql = "SELECT * FROM Authors";
SqlConnection connection = new SqlConnection(connectionString);
SqlDataAdapter dataadapter = new SqlDataAdapter(sql, connection);
DataSet ds = new DataSet();
connection.Open();
dataadapter.Fill(ds, "Authors_table");
connection.Close();
dataGridView1.DataSource = ds;
dataGridView1.DataMember = "Authors_table";
}
}
}
I`ve written some code to establish a connection to SQL Server, then execute select procedure to take all data from my data table in SQL server, but it throw a InvalidOperationException at the command of declare a new SqlDataAdapter, please help me to fix this error.
public class dBConnect
{
//create SQLconnection variable
private SqlConnection con;
//create default constructor that passing a string to con
public dBConnect()
{
try
{
con = new SqlConnection(#"Server=Trump\SQLEXPRESS;
Database=Demo;User Id=sa;Password = stevejobs;");
}
catch(Exception exCon)
{
Console.WriteLine("Unable to connect to database: {0}", exCon);
}
}
//create Select method to Pour the data into the DataTable
public DataTable SelectAll(string procName, SqlParameter[] para = null)
{
//create a DataTable to store Data from DB
DataTable dt = new DataTable();
//create SQLCommand
SqlCommand cmd = new SqlCommand(procName, con);
//declare that cmdType is sp
cmd.CommandType = CommandType.StoredProcedure;
//input parameter of cmd
if (para != null)
cmd.Parameters.AddRange(para);
//create dataAdapter object
//InvalidOperationException was thrown at here
SqlDataAdapter da = new SqlDataAdapter(cmd);
//declare that cmd is select command of da
da.SelectCommand = cmd;
//use try/catch/finally to establish a connection
try
{
con.Open();
da.Fill(dt);
}
catch(Exception sqlEx)
{
Console.WriteLine(#"：Unable to establish a connection: {0}", sqlEx);
}
finally
{
con.Close();
con.Dispose();
}
return dt;
}
}
}
You should:
cmd.CommandText = "your Stored Procedure here.";
cmd.CommandType = CommandType.StoredProcedure;
//input parameter of cmd
if (para != null)
cmd.Parameters.AddRange(para);
//create dataAdapter object
Put your con.Open(); above
or
Just take a look at this steps
DataTable dt = new DataTable();
using (SqlConnection con = new SqlConnection(connectionString))
{
con.Open();
using (SqlCommand cmd = con.CreateCommand())
{
//sample stored procedure with parameter:
// "exec yourstoredProcedureName '" + param1+ "','" + param2+ "'";
cmd.CommandText = "Your Stored Procedure Here";
cmd.CommandType =CommandType.StoredProcedure;
using (SqlDataAdapter adp = new SqlDataAdapter(cmd))
{
adp.Fill(dt);
return dt;
}
}
}
Cleaning up your code a bit here:
public DataTable SelectAll(string procName, SqlParameter[] para = null)
{
DataTable dt = new DataTable();
try
{
using (SqlConnection con = new SqlConnection(connString))
{
con.Open();
using (SqlCommand cmd = new SqlCommand(procName, con))
{
cmd.CommandType = CommandType.StoredProcedure;
if (para != null)
cmd.Parameters.AddRange(para);
using (SqlDataAdapter da = new SqlDataAdapter(cmd))
{
da.Fill(dt);
}
}
}
}
catch (Exception sqlEx)
{
Console.WriteLine(#"：Unable to establish a connection: {0}", sqlEx);
}
return dt;
}
This is what I have so far:
static void Main(string[] args)
{
DataTable t = new DataTable();
string connetionString = null;
SqlConnection cnn ;
connetionString = "Data Source=local.url;Initial Catalog=databasename;User ID=username;Password=password";
cnn = new SqlConnection(connetionString);
string sql = "SELECT * FROM shiplabels";
SqlDataAdapter a = new SqlDataAdapter(sql, cnn);
try
{
cnn.Open();
a.Fill(t);
cnn.Close();
}
catch (Exception ex)
{
Console.WriteLine ("Can not open connection ! ");
}
}
I want to connect to this Microsoft DB and pull data from it. I am having trouble just getting this to work! When I use this code datatable t has 0 rows where it should come back with a few hundred. I'm clearly missing something simple here?
DataTable dt = new DataTable();
SqlDataAdapter sqlAdtp = new SqlDataAdapter();
string connectionString = "Data Source=local.url;Initial Catalog=databasename;User ID=username;Password=password";
string sql = "SELECT * FROM shiplabels";
using (SqlConnection conn = new SqlConnection(connectionString))
{
using (SqlCommand cmd = new SqlCommand(sql, conn))
{
cmd.CommandType = CommandType.Text;
try
{
sqlAdtp.SelectCommand = cmd;
sqlAdtp.Fill(dt);
}
catch (Exception ex)
{
}
}
}
First, you don't need to open the connection when using SqlDataAdapter.
Also, you forgot the CommandType.
This should work fine for you.
using System;
using System.Windows.Forms;
using System.Data;
using System.Data.SqlClient;
namespace WindowsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
string connetionString = null;
SqlConnection sqlCnn ;
SqlCommand sqlCmd ;
SqlDataAdapter adapter = new SqlDataAdapter();
DataSet ds = new DataSet();
int i = 0;
string sql = null;
connetionString = "Data Source=ServerName;Initial Catalog=DatabaseName;User ID=UserName;Password=Password";
sql = "Select * from product";
sqlCnn = new SqlConnection(connetionString);
try
{
sqlCnn.Open();
sqlCmd = new SqlCommand(sql, sqlCnn);
adapter.SelectCommand = sqlCmd;
adapter.Fill(ds);
for (i = 0; i <= ds.Tables[0].Rows.Count - 1; i++)
{
MessageBox.Show(ds.Tables[0].Rows[i].ItemArray[0] + " -- " + ds.Tables[0].Rows[i].ItemArray[1]);
}
adapter.Dispose();
sqlCmd.Dispose();
sqlCnn.Close();
}
catch (Exception ex)
{
MessageBox.Show("Can not open connection ! ");
}
}
}
}
protected void Page_Load(object sender, EventArgs e)
{
SqlConnection con = new SqlConnection(#"Data Source=.\SQLEXPRESS;AttachDbFilename=D:\ExportPagetoPDFinASP.Net\App_Data\abcc.mdf;Integrated Security=True;User Instance=True");
con.Open();
SqlCommand cmd = new SqlCommand();
cmd.CommandText = "SELECT * FROM cookbook";
cmd.Connection = con;
cmd.ExecuteReader();
}
Not able to fetch data. i don't know what is wrong.
ExecuteReader would return you a DataReader, you need to iterate it and get rows from your command.
You can also use a DataTable to fill the rows from DataReader like:
DataTable dt = new DataTable();
dt.Load(cmd.ExecuteReader());
You can have the following code:
using (SqlConnection con = new SqlConnection(#"Data Source=.\SQLEXPRESS;AttachDbFilename=D:\ExportPagetoPDFinASP.Net\App_Data\abcc.mdf;Integrated Security=True;User Instance=True"))
{
con.Open();
using (SqlCommand cmd = new SqlCommand())
{
cmd.CommandText = "SELECT * FROM cookbook";
cmd.Connection = con;
DataTable dt = new DataTable();
dt.Load(cmd.ExecuteReader());
}
}
Consider using using statement with your Connection and Command objects.
You can iterate rows returned from DataReader like:
SqlDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
Console.WriteLine(String.Format("{0}", reader[0])); //prints first column
}
public string Log(int userResult)
{
string result = "result saved";
using (var conn = new SqlConnection("Data Source=XXXX;InitialCatalog=XXXX;Integrated Security=True"))
{
using (var cmd = new SqlCommand())
{
cmd.CommandText = "dbo.setCalculatorResult";
cmd.CommandType = CommandType.StoredProcedure;
cmd.Connection = conn;
cmd.Parameters.AddWithValue("RESULT", userResult);
if (conn.State != ConnectionState.Open)
conn.Open();
int rowCount = cmd.ExecuteNonQuery();
if (rowCount == 0)
result = "there was an error";
}
}
return result;
}
and also consider using procs
So i have code that can call a string from database that works perfectly for my label but when i try to call an integer it doesn't work. How can i reformat the code below to work for an integer?
string MoneySaved = null;
string sql = "Select Distinct(Tester) From VExecutionGlobalHistory Where Tester = 'strUserName'";
string connString = "myconnectionstringgoeshere";
using (SqlConnection conn = new SqlConnection(connString))
{
conn.Open();
using (SqlCommand command = new SqlCommand(sql, conn))
{
SqlDataReader reader = command.ExecuteReader();
while (reader.Read())
{
MoneySaved = reader[0] as string;
MoneySavedLabel.Text = MoneySaved;
//break for single row or you can continue if you have multiple rows...
break;
}
}
conn.Close();
}
Here is what worked:
string MoneySaved = null;
string sql = "Select Distinct(Tester) From VExecutionGlobalHistory Where Tester = 'strUserName'";
string connString = "myconnectionstringgoeshere";
using (SqlConnection conn = new SqlConnection(connString))
{
conn.Open();
using (SqlCommand command = new SqlCommand(sql, conn))
{
SqlDataReader reader = command.ExecuteReader();
while (reader.Read())
{
MoneySaved = reader[0].ToString();
MoneySavedLabel.Text = MoneySaved;
//break for single row or you can continue if you have multiple rows...
break;
}
}
conn.Close();
}