3

In the following code, used to get a list of products in a particular line, the command only returns results when I hard code (concatenate) productLine into the SQL. The parameter substitution never happens.

            + "lineName = '@productLine' "                       
            + "and isVisible = 1 ";
        MySqlDataAdapter adap = new MySqlDataAdapter(sql, msc);
        adap.SelectCommand.Parameters.Add("@productLine", productLine);
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4 Answers 4

Reset to default
7 
        + "lineName = ?productLine "                       
        + "and isVisible = 1 ";
    MySqlDataAdapter adap = new MySqlDataAdapter(sql, msc);
    adap.SelectCommand.Parameters.Add("?productLine", productLine);
  1. Remove the apostrophes (').
  2. Change @ to ?, which is the prefix of parameters in MySql queries.
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2

Remove the apostrophes (spelling?). The ' around the parameter. They should not be needed.

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3 Comments

If they value is a string they are.
Had to mark back up since actually the poster is correct and Mr Stevenson-Leggett is mistaken
That is an important point about parameters. You don't have to worry about encapsulating strings or formatting dates and all that.
0

like he said

+ "lineName = '@productLine' "

should be

+ "lineName = @productLine "
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0

That's correct it never happens you have

  • "lineName = '@productLine' "

try

  • "lineName = @productLine " instead as @productLine will already be declared as a string type the quotes will be added secretly. You however are actually passing the string @productLine and not the variable value.
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