CODEWITHSUNDEEP
c#sqlselect
Khaled Mohamed
Khaled Mohamed

Reputation: 217

Select from a table in for loop

for (int i = 0; i < final_query.Length; i++)
{
   con.Open();

   SqlCommand cmd=new SqlCommand("SELECT * fROM TableFFF WHERE Data="+final_query[i]);

   SqlDataReader rdr = cmd.ExecuteReader();

   while (rdr.Read())
   {
      string PatientName = (string)rdr[" Data "];
   }
}

I got that error

ExecuteReader: Connection property has not been initialized.

on this line 

SqlDataReader rdr = cmd.ExecuteReader();

How can i fix it?

Upvotes: 0

Views: 149

Answers (2)

Steve
Steve

Reputation: 216293

You need to pass the Connection to the SqlCommand

SqlCommand cmd=new SqlCommand("SELECT * fROM TableFFF WHERE Data="+final_query[i], con);

But there are other errors:

  • The call to con.Open() should be outside of the For loop

  • Use and reuse Parameters, not string concatenation

    con.Open();   
SqlCommand cmd=new SqlCommand("SELECT * fROM TableFFF WHERE Data=@data", con);   
cmd.Parameters.AddWithValue("@data", 0); // Supposing final_query[i] is an Int32
for (int i = 0; i < final_query.Length; i++)   
{   
    cmd.Parameters["@data"].Value = final_query[i];   
    SqlDataReader rdr = cmd.ExecuteReader();   
    while (rdr.Read())   
    {   
        string PatientName = (string)rdr[" Data "];   
    }   
}

And it is still not clear what you are supposing to do with the PatientName after the first round

Upvotes: 4

Arnoud Kooi
Arnoud Kooi

Reputation: 1747

You arnt telling the sqlcommand to use the connection con try

SqlCommand("SELECT * fROM TableFFF WHERE Data="+final_query[i], con);

Though it seems this isnt very good coding, and could use some redesign....

Upvotes: 0

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