How to solve must declare the scalar variable on SQL insert command?

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C#

protected void Add_Click(object sender, EventArgs e)
      {


          string constr = ConfigurationManager.ConnectionStrings["ApplicationServices"].ConnectionString;
          SqlConnection con = new SqlConnection(constr);
          //SqlCommand cmd = new SqlCommand("insert into Student values('" + RegNo.Text + "','" + Name.Text + "','" + Address.Text + "')");
          SqlCommand cmd = new SqlCommand("insert into Student(@RegNo,@Name,@Address,@CreatedTime) values(@RegNo,@Name,@Address,Getdate())");

          cmd.Connection = con;
          con.Open();

          cmd.ExecuteNonQuery();
          con.Close();

      }

What I have tried:

here am try to insert records . i have 3 textboxes namely RegNo,Name,Address and in my table I have $ columns RegNo,Name,Address,CreatedTime. in my code the following error encountered .
Must declare the scalar variable @RegNo .
what to do.

Posted 1-Feb-18 20:20pm

Member 13650918

Updated 1-Feb-18 20:56pm

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Richard Deeming 2-Feb-18 10:25am

Further to solution 1, you also have a syntax error in your SQL statement. It should be:

insert into Student(RegNo,Name,Address,CreatedTime) values(@RegNo,@Name,@Address,Getdate())

The first list in brackets is the list of columns you're inserting to. By prefixing them with @, you're trying to use the parameter values instead.

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OriginalGriff · Answer 1 · 2018-02-01T20:55:00

When you create a parameterised query - and that is exactly the right way to do SQL operations - you have to also create a Parameter which contains teh value you wish to pass to SQL. It's a bit like calling a method in C#. You define it

C#

public int DoInsert(int regNo, string name, string address, DateTime insertDate)
   {
   ...
   }

But when you call it, you must provide the values:

C#

int rowsAffected = DoInsert(666, "Mike Smith", "2 Main Street, Kentucky", DateTime.Now);

If you miss out any parameters, you get a compiler error.
SQL is the same.
Add a line for each parameter:

C#

cmd.Parameters.AddWithValue("@NameOfParameterInSQLCommand", valueIWantInTheColumn);

And it'll start to work.