getting error as Must declare the scalar variable "@tea_id"

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in my Question table colums are Question_id,tea_question,teacher_id,tea_answer.
i want to display only selected teacher_id's Questions on a label so how can i solve it
I am writing query for online Examination so each time student click on next button only only that teacher_id's Question should be display on label.
i tried following code but it gives me an Exception as "Must declare the scalar variable "@tea_id"."

//code is given below

public partial class WebForm9 : System.Web.UI.Page
    {
       
        SqlCommand cmd = new SqlCommand();
     
       DataTable dt = new DataTable();
        DataRow drr;
     static int i = 0;
  public void Page_Load(object sender, EventArgs e)
        {
           String tea_id = Convert.ToString(TextBox2.Text);
            SqlDataAdapter da = new SqlDataAdapter("select * from Question where Teacher_id=@tea_id ", con);
           da.Fill(dt);
            drr = dt.Rows[i];

            //Label2.Text = "Write question below in Textbox  click next to get questoion";
               
           // i++;
        }
           public void Button2_Click(object sender, System.EventArgs e)
        {
            
          //  Label2.Text = Convert.ToString(dr[2]);
           
            //Label3.Text = Convert.ToString(dr[3]);
            //TextBox3.Text = Convert.ToString(dr[2]);
            //TextBox4.Text = Convert.ToString(dr[3]);
                                 if (i == (dt.Rows.Count - 1))
            {
                Response.Write("Last record !");
            }
            else
            {
                //i = 0;
               i++;
             
            }
                                // drr = dt.Rows[i];
                                 Label3.Text = Convert.ToString(drr[0]);
                                 Label2.Text = Convert.ToString(drr[2]);
 
                      //Label2.Text = Convert.ToString(dr[2]);
                                // i = 0;
                                 con.Close();
       }
}
}

Posted 22-Mar-14 3:54am

swati gapat

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CHill60 · Answer 1 · 2014-03-22T04:00:00

In the line

SQL

SqlDataAdapter da = new SqlDataAdapter("select * from Question where Teacher_id=@tea_id ", con);

you have declared the variable @tea_id but you have not provided the parameter to the command
e.g.

cmd.Parameters.Add(new SqlParameter("tea_id", tea_id));

There is more wrong than just this so have a look here for a tutorial[^] on using parameterised queries

[EDIT] In response to OP comment...
Instead of String tea_id = Convert.ToString(TextBox2.Text); (by the way Convert.ToString was unnecessary TextBox2.Text is already a string) you probably want something like long tea_id = long.Parse(this.textBox1.Text);
Because tea_id was declared as string the parameter will have surrounded it by single quotes when inserting the variable into the sql string

Krunal Rohit · Answer 2 · 2014-03-22T04:16:00

Solution 2

As the error itself says something,

Quote:
"Must declare the scalar variable "@tea_id"

. You need to declare that parameter for the given command.

I have changed little bit of your code, see below

C#

int tea_id = int.Parse(TextBox2.Text);
SqlCommand cmd = new SqlCommand("select * from Question where Teacher_id=@tea_id", con);
cmd.Parameters.AddWithValue("@tea_id", tea_id);
SqlDataAdapter da = new SqlDataAdapter(cmd);
da.Fill(dt);
// rest of your code...

-KR

Posted 22-Mar-14 4:16am

Krunal Rohit

Updated 22-Mar-14 7:57am

v2

Comments

swati gapat 22-Mar-14 12:53pm

now getting error as
Error converting data type nvarchar to numeric.at line da.Fill(dt);

Krunal Rohit 22-Mar-14 13:56pm

int id = int.Parse(TextBox2.Text);
// rest of the code is same...

-KR

Peter Leow · Answer 3 · 2014-03-22T04:22:00

change this

 SqlDataAdapter da = new SqlDataAdapter("select * from Question where Teacher_id=@tea_id ", con);
da.Fill(dt);

to

string commandText = "SELECT * from Question WHERE Teacher_id=@tea_id";
using (SqlConnection connection = new SqlConnection(connectionString))
{
    using (SqlCommand command = new SqlCommand(commandText, con))
    {
        command.Parameters.AddWithValue("@tea_id", tea_id);
        SqlDataAdapter da = new SqlDataAdapter(command);
        DataTable dt = new DataTable();
        da.Fill(dt);
        // your other code...
    }
}

Er. Puneet Goel · Answer 4 · 2014-03-22T09:07:00

Hi,
when ever you pass any parameter/variable to the SQL, please consider the data type of the column for which you are passing this. SO it is always suggested that parameter with datatype mentioned.

SQL

cmd.Parameters.Add("@InputParm", SqlDbType.NVarChar, 12).Value = "Sample Value";

Doing this will avoid your chances of getting error at the receiving end i.e. Sql Server

**Nirav Prabtani** · Answer 5 · 2014-03-22T08:45:00

You have to add command parameter like that.. :)

C#

command.Parameters.AddWithValue("@tea_id", tea_id);

So the final code is...

C#

int tea_id = int.Parse(TextBox2.Text);
SqlCommand cmd = new SqlCommand("select * from Question where Teacher_id=@tea_id", con);
cmd.Parameters.AddWithValue("@tea_id", tea_id);
SqlDataAdapter da = new SqlDataAdapter(cmd);
da.Fill(dt);
//Remaining your code...

getting error as Must declare the scalar variable "@tea_id"

5 solutions

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