The following code does not work. There is only 1 row in this table. How do I just get the statement that the sql would return?:
SqlConnection conn = new SqlConnection(connectionStringArg);
SqlCommand command = new SqlCommand("select applicationname from tbl_settings");
command.Connection = conn;
conn.Open();
string simpleValue = command.ExecuteReader()[0].ToString();
conn.Close();
return simpleValue;
Okay any help on how to achieve this relatively simple task would be great.
Since there's only a single value returned, you could do this:
string value = (string)command.ExecuteScalar();
If you need more than the first column from the first row returned, you'll need to use ExecuteReader(). See driis' answer.
The DataReader can't be indexed like that. You need something like:
using(conn)
using(var reader = command.ExecuteReader())
{
reader.Read();
string simpleValue = reader.GetString(0);
}
The general idea is to advance the reader for each record (using Read), then you can read values from the row. As pointed out in another answer, if you know there is only one single value in the result set, command.ExecuteScalar() gives you just that.
You have to call the Read method on a DataReader returned from ExecuteReader to get to the first row. Something like this:
SqlDataReader rdr = command.ExecuteReader();
if (rdr.Read())
...
You'd do e.g.
using(SqlConnection conn = new SqlConnection(connectionStringArg))
using(SqlCommand command = new SqlCommand("select applicationname from tbl_settings")) {
command.Connection = conn;
conn.Open();
SqlDataReader reader = command.ExecuteReader();
if(reader.read()) {
return reader.GetString(0);
}
return null;
}
For a single string you want to use ExecuteScalar to get a single value and then attempt to cast it to string.
From doc: Executes the query, and returns the first column of the first row in the result set returned by the query. Additional columns or rows are ignored.
Example:
string result = command.ExecuteScalar() as string;
For small stuff I often find LINQ2SQL the easiest to set up and use. This tutorial should get you up and running in a few minutes. For bigger projects LINQ2SQL is considered obsolete, see this question for discussion and alternatives.
Check DataReader.Read() you need to call it.
string applicationname = "";
using(var reader = command.ExecuteReader())
{
reader.Read();
applicationname = reader.GetString(reader.GetOrdinal("applicationname"));
}
var query_result = com.ExecuteScalar() as string;
if (!string.IsNullOrEmpty(query_result )) // do your thing here...
Related
I have a problem - I want to get value from my SQL Server select but it returns:
System.Data.SqlClient.SqlDataReader
Code:
static SqlConnection sqlconnection = new SqlConnection("Data Source=XXXX;Initial Catalog=XXXX;Integrated Security=True");
static SqlCommand sqlcommand = new SqlCommand("SELECT * FROM XXX where XXX = 'XXXX'", sqlconnection);
public static string DBSQL()
{
// connect to database
sqlconnection.Open();
// execute
SqlDataReader myReader = sqlcommand.ExecuteReader();
// return valueAC
return myReader.ToString();
}
You missed a few steps. Always consult the examples provided by the vendor. In particular you're trying to return the reader itself, but instead you need to read data from it. Something like this:
SqlDataReader myReader = sqlcommand.ExecuteReader();
try
{
if (myReader.HasRows)
{
// What should you do if there's more than one row?
while (myReader.Read())
{
// Which value are you trying to read?
return myReader.GetString(0);
}
}
else
{
// What do you do when no rows are found?
return string.Empty;
}
}
finally
{
// Make sure to close the reader
myReader.Close();
}
Note a few questions in the code comments that are really up to you to answer:
You're selecting potentially zero-to-many records, but trying to return a single value. What do you want/expect to happen when the result count is anything other than 1?
You're doing a SELECT *, which is presumably getting more than one value from the database. Which value are you looking to return? (And why select more than that one?)
You can decide what to do in those various cases. But ultimately when using a DataReader you need to fetch the rows returned.
Hello everyone I am currently working on some testing project and I am having a little problem. Using selenium, I need to SendKey in specific element but instead of fixed value i need to use value (data) from my database. Can anyone help me with how to retrieve single value from database and store it in a variable so i can use it later.
Thank you and sorry for a noobish question - see code below:
SqlConnection conn = new SqlConnection();
SqlCommand command;
SqlDataReader dataReader;
conn.ConnectionString = "Server=******;Database=****;User ID=sqlserver;password=****;MultipleActiveResultSets=true;");
string query = "select RequestID, from AutomaticPayment where RequestID ='1230322'";
DataTable dt = new DataTable();
command = new SqlCommand(query, conn);
conn.Open();
dataReader = command.ExecuteReader();
dt.Load(dataReader);
driver.FindElement(By.Id("requestID")).SendKeys(VALUE FROM DATABASE);
You can use the following code
using (SqlConnection connection = new SqlConnection(_connectionString))
{
SqlDataAdapter sda = new SqlDataAdapter(query, connection);
connection.Open();
SqlCommand cmd = new SqlCommand(query, connection);
try
{
result = cmd.ExecuteScalar().ToString();
}
catch(NullReferenceException n)
{
result = "";
}
}
ExecuteScaler gets you the first column of the first row and additional columns are ignored. Use the value from result in your SendKeys()
Use conditions to limit the result:
Select data
SELECT TOP 1 RequestID FROM AutomaticPayment // Always returns 1 row
Or
SELECT RequestID FROM AutomaticPayment WHERE Id = 123 // Id must be unique to return 1 row
And maybe other ways.
Get value
var value = dt.Rows[0][1];
Or
var value = dt.Rows[0]["RequestID"];
From what i worked on with SqlCommand just do the following :
int yourId = 0;
dataReader = command.ExecuteReader()
while(dataReader.Read())
{
yourId = dataReader.GetInt32(0);
}
With that, you should have your value set to the first column of the dataReader. (that is selected thanks to your query, since you are requesting on a specific id, i guess it will return only one column
there is many other type available for Reader : Reader Microsoft Doc
And if you have in the futur many data to collect, use the ORM entity framework, work well for me
Source
EDIT :
Since you are only querying one data, maybe the solution of #work_ishaan is better than mine in this case, check it out.
Ok either I'm really tired or really thick at the moment, but I can't seem to find the answer for this
I'm using ASP.NET and I want to find the amount of rows in my table.
I know this is the SQL code: select count(*) from topics, but how the HECK do I get that to display as a number?
All I want to do is run that code and if it = 0 display one thing but if it's more than 0 display something else. Help please?
This is what I have so far
string selectTopics = "select count(*) from topics";
// Define the ADO.NET Objects
SqlConnection con = new SqlConnection(connectionString);
SqlCommand topiccmd = new SqlCommand(selectTopics, con);
if (topiccmd == 0)
{
noTopics.Visible = true;
topics.Visible = false;
}
but I know I'm missing something seriously wrong. I've been searching for ages but can't find anything.
PHP is so much easier. :)
Note that you must open the connection and execute the command before you can access the result of the SQL query. ExecuteScalar returns a single result value (different methods must be used if your query will return an multiple columns and / or multiple rows).
Notice the use of the using construct, which will safely close and dispose of the connection.
string selectTopics = "select count(*) from topics";
// Define the ADO.NET Objects
using (SqlConnection con = new SqlConnection(connectionString))
{
SqlCommand topiccmd = new SqlCommand(selectTopics, con);
con.Open();
int numrows = (int)topiccmd.ExecuteScalar();
if (numrows == 0)
{
noTopics.Visible = true;
topics.Visible = false;
}
}
ExecuteScalar is what you're looking for. (method of SqlCommand)
Btw, stick with C#, there's no way PHP is easier. It's just familiar.
You need to open the connection
This might work :
SqlConnection sqlConnection1 = new SqlConnection("Your Connection String");
SqlCommand cmd = new SqlCommand();
SqlDataReader reader;
cmd.CommandText = "select count(*) from topics";
cmd.CommandType = CommandType.Text;
cmd.Connection = sqlConnection;
sqlConnection1.Open();
reader = cmd.ExecuteReader();
// Data is accessible through the DataReader object here.
sqlConnection1.Close();
Similar Question: C# 'select count' sql command incorrectly returns zero rows from sql server
I am having a problem is getting a value from mysql using c#. The connection string is right, but it throws the following error: Invalid attempt to access a field before calling Read()
Can anyone tell me the problem which occurs in the code below
string strConnection = ConfigurationSettings.AppSettings["ConnectionString"];
MySqlConnection connection = new MySqlConnection(strConnection);
MySqlCommand command = connection.CreateCommand();
MySqlDataReader reader;
command.CommandText = "SELECT application_domain_name FROM `test`.`application_domains` WHERE idapplication_domains = " + reference;
connection.Open();
reader = command.ExecuteReader();
lblApplicationDomain.Text = reader.GetString(0);
connection.Close();
You must call reader.Read() before accessing the results.
Before you do that, the reader 'cursor' will be placed before the first element. Placing the cursor before the first element will make the behavior consistent even if the result set is empty.
You need to call reader.Read() at least once. Like a normal SqlDataReader, the pattern is like so:
while(reader.Read())
{
.. Do Stuff
}
while(sqlDataReader.MoveNext())
{
.. Do Stuff
}
I need syntax help with the following code logic:
I have a code block that gets email address from the database. The email addresses need to be assigned to a string variable strEmailAddress with a comma seperation
My code is:
SqlConnection conn = new SqlConnection(strConn);
string sqlEmailAddress = "usp_Get_Email_Address";
SqlCommand cmdEmailAddr = new SqlCommand(sqlEmailAddress, conn);
cmdEmailAddr.CommandType = CommandType.StoredProcedure;
con.Open();
SqlDataReader sqlDREmailAddr = cmdEmailAddr.ExecuteReader();
How can I loop through the records and store the results in strEmailAddress seperated by comma?
while (sqlDREmailAddr.Read())
{
//...process each row here
}
I would also wrap the reader in a using statement to make sure it is closed properly:
using (SqlDataReader sqlDREmailAddr = cmdEmailAddr.ExecuteReader())
{
}
Depending on what the columns in your dataset is named, reading values from each record will look something like this (update: now with all addresses merged):
var emailAddress = new StringBuilder();
var emailAddressOrdinal = sqlDREmailAddr.GetOrdinal("EmailAddress");
while (sqlDREmailAddr.Read())
{
if (emailAddress.Length > 0)
emailAddress.Append(',');
emailAddress.Append(sqlDREmailAddr.GetString(emailAddressOrdinal));
}
Use the SqlDataReader.Read method:
while (sqlDREmailAddr.Read())
{
...
// Assumes only one column is returned with the email address
strEmailAddress = sqlDREmailAddr.GetString(0);
}
while (sqlDREmailAddr.Read())
{
// handle row here
}
This is what you're looking for....
using (SqlConnection conn = new SqlConnection(strConn)){
string sqlEmailAddress = "usp_Get_Email_Address";
using (SqlCommand cmdEmailAddr = new SqlCommand(sqlEmailAddress, conn)){
cmdEmailAddr.CommandType = CommandType.StoredProcedure;
conn.Open(); // Typo Glitch!
using (SqlDataReader sqlDREmailAddr = cmdEmailAddr.ExecuteReader()){
while(sqlDREmailAddr.Read()){
if (!sqlDREmailAddr.IsDBNull(sqlDREmailAddr.GetOrdinal("emailAddr"))){
// HANDLE THE DB NULL...
}else{
strEmailAddress = sqlDREmailAddr.GetSqlString(sqlDREmailAddr.GetOrdinal("emailAddr"));
// Do something with strEmailAddr...
}
}
}
}
}
Notice:
A typo glitch on the conn variable...
A check is made to ensure that the Database value returned is not NULL
A call is made to GetOrdinal to return the column based on emailAddr string value that corresponds to the column from the query for SQL Select...which is an int type) as the parameter for GetSqlString..
Edit: Thanks to John Saunders for pointing out a blooper!
Edit#2: Thanks to Peter Lillevold for pointing out a mis-spelling...
Hope this helps,
Best regards,
Tom.