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The DataSet result is always empty in C#

I am retrieving particular column value using DataSet.
This is my code:
public DataSet GetRedirectURL(string emailId)
{
DataSet ds = new DataSet();
using (SqlConnection con = new SqlConnection(#"Connection_String_Here"))
{
con.Open();
SqlCommand sqlComm = new SqlCommand("usp_Login", con)
{
CommandType = CommandType.StoredProcedure
};
sqlComm.Parameters.AddWithValue("#EmailId", emailId);
SqlDataAdapter da = new SqlDataAdapter
{
SelectCommand = sqlComm
};
da.Fill(ds);
}
return ds;
}
I have also used DataTable instead of it but the same result.
I have checked my Stored Procedure and when I pass Parameter it shows Data. So, nothing wrong with the SP. But the Table doesn't show any data and is always empty as shown below:
What am I missing? Any help would be appreciated.

I'd suggest you to first evaluate the content of your DataSet. For instance, type in your Immediate Window (or add a quick watch) to check ds.Tables[0].Rows.Count. Basically, to assert your DataSet has been properly filled with the contents fetched from the database, and focus on the data assignment from the DataSet to the grid object you're using to display it.
Also, the .Fill() method has a returning object which is an int representing the amount of rows that have been successfully filled into the target object. For instance:
int result = da.Fill(ds);
Check the value of result after the .Fill() method has been executed.
Finally, I guess you're using a DataGridView object to visualize the results. If so, how are you binding data? Should be something like:
dataGridView1.DataSource = ds.Tables[0];
PS: As I've read in other comments, no, you don't need to execute the .Open() method on the connection. That's not necesarry, it's done implicitely when using the (using SqlConnection conn = SqlConnection..)

Better way to get json data from relational databases?

I don't know my title is understandable but actually I want to know which one is better?
1-Creating object class and get data from mssql db with loop
2-Getting data from sql db with json format
3-Something else..
I think, loop can be slow when working with big datas. However maybe using json path can be slower than loop.
Example for 1 (CREATING OBJECT IN LOOP)
List<objExample > retVal = new List<objExample >();
objExample item;
SqlConnection con = new SqlConnection("CONNECTION STRING");
SqlDataAdapter da;
SqlCommandcmd;
da = new SqlDataAdapter("Select a,b from table", con);
con.Open();
DataTable dt = new DataTable();
da.Fill(dt);
con.Close();
foreach (DataRow itemdr in dt.Rows)
{
item = new objExample();
item.A= itemdr["a"].ToString();
item.B= itemdr["b"].ToString();
item.HasError = false;
retVal.Add(item);
}
return retVal;
Example for 2 (FOR JSON PATH)
List<objExample > retVal;
SqlConnection con = new SqlConnection("CONNECTION STRING");
SqlDataAdapter da;
SqlCommandcmd;
da = new SqlDataAdapter("Select a,b from table for json path", con);
con.Open();
DataTable dt = new DataTable();
da.Fill(dt);
con.Close();
string _json = dt.Rows[0][0].ToString();
retVal = JsonConvert.DeserializeObject<List<objExample>>(_json);
return retVal;
I tried both of them with small data but it didn't satisfy me.
PS : I wrote codes in my mind. Sorry about wrong codes and bad English.
Please guide to me. Thanks.

Just to be clear, are you reading the complete table?
If the goal is to get data that is stored within the json, and maybe perform some queries on it a NoSQL DB seems more appropriate that a SQL one.

Count the number of commands that are dependent on the number of rows. Kind of how we do the Big O Complexity.
I would do something like:
using (var sqlCommand = new SqlCommand("Select a,b from table for json path", con))
{
try
{
using (var reader = sqlCommand.ExecuteReader())
{
while (reader.Read())
{
item = new objExample();
item.A= reader["a"].ToString();
item.B= reader["b"].ToString();
item.HasError = false;
retVal.Add(item);
}
}
}
}
Keep in mind that the sql connection will remain open while you are doing this so its judgement call if you want to do this after loop or in the loop.
And the da.Fill or using the above is same internally, still going to iterate over all rows.
As far as using json is concerned, I wouldn't do that unless you are asking if storing as Json file is a better option than in sql. That's a whole diff question.
You can use PLINQ to process the data in parallel once you have it in the list, even for your above deserialization you can try PLINQ.

filling result of data adapter to my own data set?

before start my question I need to mention I'm c++ programmer not c#, so maybe my code syntax seems wrong. I'm amateur and need improvement!;)
I have a question (maybe it's an idea instead of question) about working with result of data adapter output.
let's take a look at theses lines:
public DataSet CollectData()
{
DataSet result = new DataSet();
using (SqlConnection conn = new SqlConnection(connectionString))
using (SqlCommand cmd = new SqlCommand("dbo.StoredProc1", conn))
{
cmd.CommandType = CommandType.StoredProcedure;
IDataAdapter adapter = new SqlDataAdapter(cmd);
adapter.Fill(result);/// filling a dataset
return result;
}
}
as you see this function fill a data set and return it.
Anywhere that I want to use this object I should loop through it like this:
DataSet dataSet = DataObj.CollectData(); /// above function!
string token;
string lemma;
foreach (DataRow row in dataSet.Tables[0].Rows)
{
token = ((string)row["Token"]);
lemma = ((string)row["Lemma"]);
...
//// TODO: ex. write to file
}
but, I have a class that it demonstrate this stored objects.
a class like this:
public class Lexeme
{
private int tokenId = -1;
private string token;
private string lemma;
/// some get and set functions!
}
as you see this class holds an object (it's something like a wrapper for stored object inside of database tables)
So I want to know is there anyway to return a list of this object (Lexeme here) instead of dataset? I mean something with efficient memory usage. because i work with huge amount of data.
for example something like this:
public MYDATASET CollectData()
{
MYDATASET result = new MYDATASET ();
using (SqlConnection conn = new SqlConnection(connectionString))
using (SqlCommand cmd = new SqlCommand("dbo.StoredProc1", conn))
{
cmd.CommandType = CommandType.StoredProcedure;
IDataAdapter adapter = new SqlDataAdapter(cmd);
adapter.Fill(result);/// filling a dataset
return result;
}
}
dataset can be inherited?

You can use a Typed Dataset instead of your own object. This allows you to fill a dataset easily, but also have strongly typed columns and the ability to access each property easily within a row. Go to the Add New Item window of Visual Studio and add a Dataset. Add a new table using the designer, and add the columns that are being returned from your sql query. Go to the properties window on each column and specify the type (int, string, etc).
From there, when you're loading the dataset, create a new object of your dataset type, and fill it like you were before:
public MyTypedDataset GetMyDataSet()
{
MyTypedDataset ds = new MyTypedDataset();
using (SqlConnection conn = new SqlConnection(connectionString))
using (SqlCommand cmd = new SqlCommand("dbo.StoredProc1", conn))
{
cmd.CommandType = CommandType.StoredProcedure;
IDataAdapter adapter = new SqlDataAdapter(cmd);
adapter.Fill(ds.Table1);
return result;
}
}
With a typed dataset there is a property for each table item you created in the designer. (By default I believe it is named Table1?)
Now, when accessing your data, you can do
MyTypedDataset ds = GetMyDataSet();
string myToken = ds.Table1.Rows[0].Token;
string myLemma = ds.Table1.Rows[0].Lemma;
Or in a foreach:
MyTypedDataset ds = GetMyDataSet();
foreach(var row in ds.Table1)
{
string myToken = row.Token;
string myLemma = row.Lemma;
}
This isn't quite as good as getting a list of your object back, but it's almost there. If you want a list of your own object, you'll most likely need to use an Object Relational Mapper, such as Entity Framework or NHibernate.

Combobox add rows dynamically and dropdown from SQL Server stored procedure

This is basically a search tool. When I type some thing in a combobox, the combobox drops down and will show me suggestions (something like Google search bar)
I created a procedure which does some complex calculations, which take one parameter and returns some rows. Then I created a combobox event (On Update Text).
And in the event handler I wrote this code:
private void combobox_TextUpdate(object sender, EventArgs e)
{
this.combobox.Items.Clear();
DataTable List = new DataTable();
if (this.combobox.Text.Length > 0)
{
List = searchIt(combobox.text);
foreach (DataRow Row in List.Rows)
{
this.combobox.Items.Add(Row.ItemArray.GetValue(0).ToString());
}
this.combobox.DroppedDown = true;
}
}
static public DataTable searchIt(string STR)
{
string connectionString = McFarlaneIndustriesPOSnamespace.Properties.Settings.Default.McFarlane_IndustriesConnectionString;
SqlConnection con = new SqlConnection(connectionString);
DataTable DT = new DataTable();
con.Open();
SqlDataAdapter DA = new SqlDataAdapter("USE [McFarlane Industries] " +
"EXEC search " +
STR, connectionString);
DA.Fill(DT);
con.Close();
return DT;
}
The function searchIt executes the stored procedure and it returns a DataTable. The stored procedure is working fine in SQL Server Management Studio.
But in the application it is not working correctly in some cases.
When I type [space], then it throws an exception and it says stored procedure needs parameter which is not provided.
There are many other characters when I type them it throws exception that invalid character at end of string "my string".
Any suggestion how could I achieve my goal.

Call your stored procedure with sqlcommand to fill your datatable
using (SqlConnection scn = new SqlConnection(connect)
{
SqlCommand spcmd = new SqlCommand("search", scn);
spcmd.Parameters.Add("#blah", SqlDbType.VarChar, -1); //or SqlDbType.NVarChar
spcmd.CommandType = System.Data.CommandType.StoredProcedure;
using (SqlDataAdapter da = new SqlDataAdapter(spcmd))
{
da.Fill(dt);
}
}

static public DataTable searchIt(string STR)
{
string connectionString = McFarlaneIndustriesPOSnamespace.Properties.Settings.Default.McFarlane_IndustriesConnectionString;
SqlConnection con = new SqlConnection(connectionString);
DataTable DT = new DataTable();
con.Open();
SqlCommand command = new SqlCommand("Name_of_Your_Stored_Procedure",con);
command.CommandType=CommandType.StoredProcedure;
command.Parameters.Add(new SqlParameter("#parameter_name",SqlDbType.NVarChar));
command.Parameters[0].Value="Your Value in this case STR";
SqlDataAdapter DA = new SqlDataAdapter(command);
DA.Fill(DT);
con.Close();
return DT;
}
Important :
'parameter_Name' and 'Name_of_Your_Stored_Procedure' should be replaced by yours which you have in database. And value of parameter could be like "abc" (combox.Text)
Command and its type, its text are necessary.
Adding parameters depends upon your stored procedure. They can be 0,1 or more but once they are added their values must be given. conn(connection) can be passed to new SqlCmmand() or new SqlDataAdapter()
No need of things like 'use' and 'exec'
Following me and this link might be helpful in future for stored procedures
http://www.codeproject.com/Articles/15403/Calling-Stored-procedures-in-ADO-NET
Two optional Suggestions for you
use variable name 'list' instead of 'List' (you used) however you will not get problem with this name until you add a namespace using System.Collections.Generic; but you may need to use this namespace in future.
Use only list.Rows[0].ToString(); no need to get itemarray then get value when you are working with data in strings;

C# change mdb filed data type to memo and save it

I would like to change the data type in my db from "Text" to "Memo".
first of all, I didnt find the "Memo" data type in c#.
second: I got the following code to execute command in the db:
public void SQLCommand(String strSQL)
{
OleDbConnection objConnection = null;
OleDbCommand objCmd = null;
String strConnection;
strConnection = #"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + path + "\\tasks.mdb";
objConnection = new OleDbConnection(strConnection);
objConnection.ConnectionString = strConnection;
objConnection.Open();
objCmd = new OleDbCommand(strSQL, objConnection);
objCmd.ExecuteNonQuery();
objConnection.Close();
UpdateListView();
}
how can I change the 3rd column's data type and save it?
I can change the data type when form_load with this function:
public void tst()
{
conn.Open();
DataSet ds = new DataSet();
OleDbDataAdapter adapter = new OleDbDataAdapter("SELECT * from Tasks", conn);
adapter.Fill(ds);
DataTable dt = ds.Tables[0];
dt.Columns[3].DataType = System.Type.GetType("System.String");
conn.Close();
}
but with this function, it change to the data type to string > and I want memo.
also this function is no good since I need to run it everytime and if I change it permanently to memo I will just have to make a little if at the begining.
~Thanks.

String in C# is the equivalent of both Text and Memo in that it supports texts of either length.
If I understand the question correctly I think you're misunderstanding what you're actually doing in your code. When you set the DataType of the column, you're not changing the database in any way, you are just changing the datatype of a column in the DataTable instance that you've created.
If you actually want to change the structure of the database the best way would probably be to do it manually in Access, since I'm not sure if that's really supported in ADO.Net (I suppose you might be able to do it using ALTER statements). Otherwise you might be able to do it using DAO which used to be the Access/Jet way of doing things like that, but that was deprecated quite a while ago so might not work well in .Net.