C# constructing parameter query SQL - LIKE %

Question

I am trying to build SQL for a parameter query in C# for a query which will contain the LIKE %% command.

Here is what I am trying to acheive (please note that the database is Firebird)

var SQL = string.format("SELECT * FROM {0} WHERE {1} LIKE '%?%'", TABLE, NAME);
 cmd.Parameters.AddWithValue(NAME, "JOHN");

Now I have tried every single permutation to get the parameter to work, I have tried;

• Adding the % character to the parameter,

  cmd.Parameters.AddWithValue(NAME, "%" + "JOHN" + "%");
  

• or

  cmd.Parameters.AddWithValue(NAME, "'%" + "JOHN" + "%'");
  

I cannot seem to get this to work, how can I use a parameter for the LIKE query to work.

Suggestions are welcome!

Answer 1

You can't have parameters inside of a string literal in the query. Make the entire value the parameter, and add the wildcards to the string:

var SQL = string.format("SELECT * FROM {0} WHERE {1} LIKE ?", TABLE, NAME);
Cmd.Parameters.AddWithValue(NAME, "%" + "JOHN" + "%");