I'm using the following to retrieve data from a database but the sqlconnection won't open. It throws an error at scon.Open(). I'm sure it's elementary but I can't work it out.
public partial class populate : System.Web.UI.Page
{
SqlConnection scon = new SqlConnection("Data Source = localhost; Integrated Security = true; Initial Catalog = populate");
protected void Page_Load(object sender, EventArgs e) {
StringBuilder htmlString = new StringBuilder();
if(!IsPostBack)
{
using (SqlCommand scmd = new SqlCommand())
{
scmd.Connection = scon;
scmd.CommandType = CommandType.Text;
scmd.CommandText = "SELECT * FROM populate";
scon.Open();
SqlDataReader articleReader = scmd.ExecuteReader();
htmlString.Append("'Populate page:'");
if (articleReader.HasRows)
{
while (articleReader.Read())
{
htmlString.Append(articleReader["dateTime"]);
htmlString.Append(articleReader["firstName"]);
htmlString.Append(articleReader["lastName"]);
htmlString.Append(articleReader["address"]);
htmlString.Append(articleReader["details"]);
}
populatePlaceHolder.Controls.Add(new Literal { Text = htmlString.ToString() });
articleReader.Close();
articleReader.Dispose();
}
}
}
}
}
I'm using this link
https://msdn.microsoft.com/en-us/library/jj653752(v=vs.110).aspx
as one of my references. I'm also using SQLEXPRESS 2008 R2 if these information are of any help. Here's part of the error message:
Message=A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)
Would appreciate if I could get past this and move on. Thanks in advance.
If you have user instances configured on SQL Server (which is the default), you need to change your connection string to this:
Data Source=.\SQLExpress;Integrated Security=true;
initial catalog=database_Name
select * from table_name
Is your database name and table name same?
Related
I am new to msql and i am working on MySQL Workbench 8.0 CE
I am trying to bind data from database to datagridview as show below but i am getting error below
but I am able to connecto my database using MySQL Workbench 8.0 CE so the connection to up so what I can do ?
public void GetPersonData()
{
string connstr = "Server=localhost;Database=newsequesterdb;Uid=reser;Pwd=00";
string query = "SELECT * FROM NEWSEQUESTERDB.PERSON;";
using (SqlConnection conn = new SqlConnection(connstr))
{
using (SqlDataAdapter adapter = new SqlDataAdapter(query, conn))
{
DataSet ds = new DataSet();
adapter.Fill(ds);
dgv_data.DataSource = ds.Tables[0];
}
}
}
error message
System.Data.SqlClient.SqlException: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)
SqlConnection is specific to MS SQL Server. Use MySqlConnection (and associated command and data adapter classes) instead.
Note that MySqlConnection is not built in to the .NET Framework - you'll need to install it separately.
The thing is that you cannot use an SqlConnection instance nor SqlAdapter, those are intended to be SQL Server connection classes. And this you can see by the exception itself.
...(provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)
So, what's next? You should really look up to this question and may solve a few doubts.
From that question we can see that is using other references to connect to MySQL. Specifically Oracle's nugget package: MySQL.Data
using MySql.Data;
using MySql.Data.MySqlClient;
From that question example:
var dbCon = DBConnection.Instance();
dbCon.DatabaseName = "YourDatabase";
if (dbCon.IsConnect())
{
//suppose col0 and col1 are defined as VARCHAR in the DB
string query = "SELECT col0,col1 FROM YourTable";
var cmd = new MySqlCommand(query, dbCon.Connection);
var reader = cmd.ExecuteReader();
while(reader.Read())
{
string someStringFromColumnZero = reader.GetString(0);
string someStringFromColumnOne = reader.GetString(1);
Console.WriteLine(someStringFromColumnZero + "," + someStringFromColumnOne);
}
dbCon.Close();
}
when i tried to run this program in visual studio 2010 its shows an error. Like this "A network-related or instance-specific error occurred while establishing a connection to SQL server.The server was not found or was not accessible.verify that the instance name is correct and that SQL Server is configured to allow remote connections.(provider:Named pipes Provider,error:40-could not open a connection to SQL Server)"
public partial class tcregistration : Form
{
SqlConnection conn = new SqlConnection("Data Source=./SQLEXPRESS;AttachDbFilename=C:/Users/dce 3/documents/visual studio 2010/Projects/TC_Maker/TC_Maker/TC_REG.mdf;Integrated Security=True;User Instance=True");
public tcregistration()
{
InitializeComponent();
}
private void insert_Click(object sender, EventArgs e)
{
string gender = string.Empty;
if (rbmale.Checked)
{
gender = "M";
}
else if (rbfemale.Checked)
{
gender = "F";
}
string tcrecieved = string.Empty;
if (rbyes.Checked)
{
tcrecieved = "Y";
}
else if (rbno.Checked)
{
tcrecieved = "N";
}
try
{
if (conn.State == ConnectionState.Closed)
conn.Open();
SqlCommand cmd = new SqlCommand ("TCAddorUpdate",conn);
cmd.CommandType=CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("#mode","Add");
cmd.Parameters.AddWithValue("#tcnumber",txttcno.Text.Trim());
cmd.Parameters.AddWithValue("#name",txtname.Text.Trim());
cmd.Parameters.AddWithValue("#dob",dtpdob);
cmd.Parameters.AddWithValue("#religion",txtrelig.Text.Trim());
cmd.Parameters.AddWithValue("#caste",txtcaste.Text.Trim());
cmd.Parameters.AddWithValue("#sex",gender);
cmd.Parameters.AddWithValue("#doa",dtpdoa);
cmd.Parameters.AddWithValue("#regno",txtregno.Text.Trim());
cmd.Parameters.AddWithValue("#dor",dtpdor);
cmd.Parameters.AddWithValue("#dept",txtdept.Text.Trim());
cmd.Parameters.AddWithValue("#sem", combosem);
cmd.Parameters.AddWithValue("#ifqulify",txtqualified.Text.Trim());
cmd.Parameters.AddWithValue("#conduct",txtconduct.Text.Trim());
cmd.Parameters.AddWithValue("#applieddate",dtpdoapp);
cmd.Parameters.AddWithValue("#ifrecieved",tcrecieved);
cmd.Parameters.AddWithValue("#receiveddate",dtpdor);
cmd.ExecuteNonQuery();
MessageBox.Show("Data Inserted Successfully");
}
catch(Exception ex)
{
MessageBox.Show(ex.Message,"Error Message");
}
finally
{
conn.Close();
}
}
}
}
A network-related or instance-specific error occurred while establishing a connection to SQL server.The server was not found or was not accessible.verify that the instance name is correct and that SQL Server is configured to allow remote connections.(provider:Named pipes Provider,error:40-could not open a connection to SQL Server)
This is not a programming Problem, but a networking/connection string one.
Connection Strings are their own area of experetise, way outside the normal programmers knowledge. Luckily there is a page for it: https://www.connectionstrings.com/sql-server/
It turns out even when attaching, you have to supply a database name: "Why is the Database parameter needed? If the named database have already been attached, SQL Server does not reattach it. It uses the attached database as the default for the connection."
And as others mentioned, you got the wrong kind of slashes too.
Pretty off topic, but exception handling is a pet peeve of mine. And yours has some of the serioues mistakes. Like catching exception and only exposing the message. Those are 2 Cardinal sins. Thee are two article on the thematic I link often:
https://blogs.msdn.microsoft.com/ericlippert/2008/09/10/vexing-exceptions/
https://www.codeproject.com/Articles/9538/Exception-Handling-Best-Practices-in-NET
I am trying to make a connection to MySQL database from my cpanel with Visual studio, but I keep getting an error:
A network-related or instance-specific error occurred while
establishing a connection to SQL Server. The server was not found or
was not accessible. Verify that the instance name is correct and that
SQL Server is configured to allow remote connections. (provider: Named
Pipes Provider, error: 40 - Could not open a connection to SQL Server)
I have installed both MySql for Visual studio and Connector/net. I have tried with both Server Explorer and through the code using the connection string. I have added my ip to the access host list on Remote MySql in CPanel. But nothing worked.
namespace Program
{
public partial class WebForm1 : System.Web.UI.Page
{
string connectionString = #"SERVER=mydomain.net;DATABASE=mydatabasename;UID=myuser;PASSWORD=mypass";
protected void Page_Load(object sender, EventArgs e)
{
FillDropDown(DropDownList1);
}
public void FillDropDown(DropDownList dropDown)
{
try
{
using (SqlConnection sqlCon = new SqlConnection(connectionString))
{
SqlCommand sqlCmd = new SqlCommand("Select * from MyTable", sqlCon);
sqlCon.Open();
dropDown.DataSource = sqlCmd.ExecuteReader();
dropDown.DataBind();
dropDown.DataTextField = "Name";
dropDown.DataValueField = "Id";
}
}
catch(Exception ex)
{
lblError.Text = ex.Message;
}
}
}
}
The SqlConnection-object may only be used for connections to MS-SqlServers. You have to use MySqlConnection to connect to MySql-server. This also applies to the SqlCommand.
Furthermore the used connection-string is not valid for MySql ('Password' should be 'Pwd') Compare your string to https://www.connectionstrings.com/mysql/
I have the sample database Northwind installed and attached to a C# project
I'm trying to connect to the database and retrieve column names of a table in the database, but I'm getting an error while trying to open the connection, here is the code I'm using to do so:
public void connectToDB()
{
Dictionary<object, object> colns = new Dictionary<object, object>();
List<string> colnNames = new List<string>();
con = new SqlConnection("Data Source = .NorthwindDB.mdf; Integrated Security=True");
con.Open();
cmd = con.CreateCommand();
cmd.CommandText = "SELECT * FROM Products";
adapter = new SqlDataAdapter(cmd);
ds = new DataSet();
adapter.Fill(ds);
dt = ds.Tables["Products"];
foreach(DataRow dr in dt.Rows)
{
foreach(DataColumn dc in dr.Table.Columns)
{
colnNames.Add(dc.ColumnName.ToString());
}
}
foreach(string key in colnNames)
{
Console.WriteLine(key.ToString());
}
Console.ReadKey();
}
I'm getting the following error:
An unhandled exception of type 'System.Data.SqlClient.SqlException' occurred in System.Data.dll
Additional information: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)
Another thing that may help, I'm noticing that whenever I click start button to execute the code, the green plug that appears over the data connection NorthwindDB.mdf turns into red x.
Your connection string is incorrect it should be something like this:
con = new SqlConnection("Data Source=(local);" +
"Initial Catalog=NorthwindDB.mdf;Integrated Security=True");
// Or Data Source=.\\sqlexpress;
You can read more about connection strings here: Database Connectionstrings.
I'm using the following to retrieve data from a database but the SqlConnection won't open. It throws an error at scon.Open(). I'm sure it's elementary but I can't work it out.
protected void Page_Load(object sender, EventArgs e) {
SqlConnection scon = new SqlConnection("Data Source = .\\SQLEXPRESS; Database = populate.mdf; Integrated Security = true; Initial Catalog = populate");
StringBuilder htmlString = new StringBuilder();
if(!IsPostBack)
{
using (SqlCommand scmd = new SqlCommand())
{
scmd.Connection = scon;
scmd.CommandType = CommandType.Text;
scmd.CommandText = "SELECT * FROM populate";
scon.Open();
SqlDataReader articleReader = scmd.ExecuteReader();
htmlString.Append("'Populate page:'");
if (articleReader.HasRows)
{
while (articleReader.Read())
{
htmlString.Append(articleReader["dateTime"]);
htmlString.Append(articleReader["firstName"]);
htmlString.Append(articleReader["lastName"]);
htmlString.Append(articleReader["address"]);
htmlString.Append(articleReader["details"]);
}
populatePlaceHolder.Controls.Add(new Literal { Text = htmlString.ToString() });
articleReader.Close();
articleReader.Dispose();
}
}
}
}
I'm using this link https://msdn.microsoft.com/en-us/library/jj653752(v=vs.110).aspx as one of my references. I'm also using SQL Server 2008 R2 Express if these information are of any help.
Here's part of the error message:
SqlException (0x80131904): Cannot open database "populate" requested
by the login. The login failed.
Any help would be greatly appreciated.
Quoted from https://msdn.microsoft.com/en-us/library/jj653752(v=vs.110).aspx#sse, if you want to use .mdf file as a database, you should use the following connection string containing AttacheDbFileName.
<add name="ConnectionStringName"
providerName="System.Data.SqlClient"
connectionString="Data Source=.\SQLEXPRESS;AttachDbFileName=|DataDirectory|\DatabaseFileName.mdf;Integrated Security=True;User Instance=True;MultipleActiveResultSets=True" />
I solved it. All the connection string and other code was correct. The database just needed connecting to the Management Studio with some extra attention.