c# - How to use sql parameters for a select query?

Question

I need to fetch the records based on a 'like' match against a set of records,

The below query im using is not working . Does anyone knows what's wrong with the query?

 sqlCommand.CommandText =String.Format("SELECT * FROM Customer" +
                " WHERE (Name like @Name)","'%" +searchString.Trim()+"%'");
            sqlCommand.Parameters.AddWithValue("Name", searchString);

This query isnt fetching the desired records.

I'm getting the following error while running the above snippet:

Must declare the scalar variable "@Name".

Answer 1

What happens this way?

sqlCommand.CommandText = "SELECT * FROM Customer WHERE Name LIKE @Name;";
sqlCommand.Parameters.AddWithValue("@Name", "%" + searchString + "%");

You could also code it as follows to avoid all the wildcard formatting in the first place:

sqlCommand.CommandText = "SELECT * FROM Customer WHERE CHARINDEX(@Name, Name) > 0;";
sqlCommand.Parameters.AddWithValue("@Name", searchString);

If you're going to insist on doing it the unsafe way, at the very least double-up any single quotes found in searchString, e.g.

searchString.Replace("'", "''")