C# - How do you use integers in c# to indentify the the limit to select from the table from mysql

Question

Current im trying to use this im my code to try and read specific data between two different rows: example:

SELECT * 
  FROM chat 
 LIMIT 1, 20

In my c# code ive current got:

 cmd.CommandText = "SELECT * from chat LIMIT " + cCfirst + "'" + cClast + "'";

Which isnt working in my code as the data reader isn't finding anything?
how can i fix this?

Answer 1

Try not constructing string from chunks which is prone to errors

// wrong technique, do not do it: 
//   1. Can you see that "," is omitted?
//   2. Can you see that both "'" are at least redundant?  
cmd.CommandText = "SELECT * from chat LIMIT " + cCfirst + "'" + cClast + "'";

but formatting eg with a help of string interpolation (C# 6.0+):

cmd.CommandText = 
  $@"SELECT * 
       FROM chat 
      LIMIT {cCfirst}, {cClast}";

Or in case of C# 5.0-

cmd.CommandText = string.Format(
  @"SELECT * 
      FROM chat 
     LIMIT {0}, {1}", 
   cCfirst, cClast);

Make SQL being readable . Open SQL editor, debug the query, copy the query debugged into C# code, turn values into {...} placeholders (eg 1 -> {cCfirst} ; 20 -> {cClast} ).

Then use the code:

 using (MySqlConnection con = new MySqlConnection(YourCOnnectionString)) {
   con.Open();

   using (MySqlCommand cmd = new MySqlCommand()) {
     cmd.Connection = con;

     cmd.CommandText =
       $@"SELECT * 
            FROM chat 
           LIMIT {cCfirst}, {cClast}";

     using (var reader = cmd.ExecuteReader()) {
       while (reader.Read()) {
         //TODO: put relevant code here
       }
     }
   }  
 }

Answer 2

The following illustrates the LIMIT clause syntax with two arguments:

SELECT 
column1,column2,...
FROM
table
LIMIT offset , count;

In your C# code it seems you are missing comma between offset and count.

cmd.CommandText = "SELECT * from chat LIMIT " + cCfirst + "," + cClast;