Use of SqlParameter in SQL LIKE clause not working

Question

I have the following code:

const string Sql = 
    @\"select distinct [name] 
      from tblCustomers 
      left outer join tblCustomerInfo on tblCustomers.         


        

Answer 1

Just a little careful with a slight difference between Add and AddWithValue methods. I had the problem below, when I used the Add method and put the wrong SqlType parameter.

• nchar and nvarchar can store Unicode characters.
• char and varchar cannot store Unicode characters.

For example:

string query = " ... WHERE stLogin LIKE @LOGIN ";

SqlParameter p = new SqlParameter("@LOGIN", SqlDbType.Char, 255) 
{ 
    Value = "%" + login + "%" 
};

command.Parameters.AddWithValue(p.ParameterName, p.Value); //works fine!!!

command.Parameters.Add(p); // won't work

When I changed the SqlType to NVarChar, the two methods worked fine to me.

SqlParameter p = new SqlParameter("@LOGIN", SqlDbType.NVarChar, 255) 
{ 
    Value = "%" + login + "%" 
};

command.Parameters.AddWithValue(p.ParameterName, p.Value); //worked fine!!!

command.Parameters.Add(p); //worked fine!!!