Error: Must declare the scalar variable "@data"

Question

I am getting an error when execution reaches cmd.ExecuteNonQuery() which says Must declare the scalar variable:

OleDbCommand cmd = new OleDbCommand();
cmd.Connection = Connection;
cmd.CommandTimeout = 0;

string commandText = "update groups set subjectline ='" +    txtSubjectLine.Text + "',data= @data where groupid = " + ddlGroup.SelectedItem.Value + " ";
cmd.CommandText = commandText;
cmd.CommandType = CommandType.Text;

cmd.Parameters.Add("@Data",OleDbType.VarBinary);
cmd.Parameters["@Data"].Value = binarydata;               
cmd.ExecuteNonQuery();

Answer 1

Replace

string commandText = "update groups set subjectline ='" +    txtSubjectLine.Text + "',data= @data where groupid = " + ddlGroup.SelectedItem.Value + " ";

with

string commandText = "update groups set subjectline ='" +    txtSubjectLine.Text + "',data= ? where groupid = " + ddlGroup.SelectedItem.Value + " ";

that is, replace "@data" with "?" in the command text. This is how you specify parameter placeholders with OleDbCommand.

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Here's the edited original:

OleDbCommand cmd = new OleDbCommand();
cmd.Connection = Connection;
cmd.CommandTimeout = 0;

cmd.CommandText = "update groups set subjectline ='" + txtSubjectLine.Text + "', data = ? where groupid = " + ddlGroupSelectedItem.Value;
cmd.CommandType = CommandType.Text;

cmd.Parameters.Add("p1", OleDbType.VarBinary);
cmd.Parameters["p1"].Value = binarydata;

cmd.ExecuteNonQuery();