Escaping the escape character does not work – SQL LIKE Operator

Question

I have used \ as escape character for LIKE operator. I am escaping following four characters

1 % 2 [ 3 ] 4 _

When I pass the escape character as input, the query does not return a value. How can I make it work?

Data Insert

DECLARE @Text VARCHAR(MAX)
SET @Text = 'Error \\\ \\  C:\toolbox\line 180'

INSERT INTO Account (AccountNumber,AccountType,Duration,ModifiedTime) 
VALUES (198,@Text,1,GETDATE())

CODE

    static void Main(string[] args)
    {

        string searchValue1 = @"Error \\\ \\  C:\toolbox\line 180";
        string searchValue2 = @"55555";

        string result1 = DisplayTest(searchValue1);
        string result2 =  DisplayTest(searchValue2);

        Console.WriteLine("result1:: " + result1);
        Console.WriteLine("result2:: " + result2);
        Console.ReadLine();

    }}


     private static string DisplayTest(string searchValue)
    {
        searchValue = CustomFormat(searchValue);


        string test = String.Empty;
        string connectionString = "Data Source=.;Initial Catalog=LibraryReservationSystem;Integrated Security=True;Connect Timeout=30";

        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            connection.Open();
            string commandText = @"SELECT AccountType,* 
                              FROM Account 
                              WHERE AccountType LIKE @input ESCAPE '\'";
            using (SqlCommand command = new SqlCommand(commandText, connection))
            {
                command.CommandType = System.Data.CommandType.Text;
                command.Parameters.AddWithValue("@input", "%" + searchValue + "%");

                using (SqlDataReader reader = command.ExecuteReader())
                {
                    if (reader.HasRows)
                    {
                        while (reader.Read())
                        {

                            test = reader.GetString(0);
                        }
                    }
                }
            }
        }

        return test;
    }


    private static string CustomFormat(string input)
    {
        input = input.Replace(@"%", @"\%");
        input = input.Replace(@"[", @"\[");
        input = input.Replace(@"]", @"\]");
        input = input.Replace(@"_", @"\_");
        //input = input.Replace(@"\", @"\\");
        return input;
    }

REFERENCE:

1. How can I escape square brackets in a LIKE clause?
2. How to escape a string for use with the LIKE operator in SQL Server?

Answer 1

Modify your CustomFormat method like this:

private static string CustomFormat(string input)
{
    input = input.Replace(@"\", @"\\"); 
    input = input.Replace(@"%", @"\%");
    input = input.Replace(@"[", @"\[");
    input = input.Replace(@"]", @"\]");
    input = input.Replace(@"_", @"\_");
    return input;
}