Question

From my ASP.NET application I want to issue this query to MySQL

SELECT * FROM responses WHERE field_id LIKE '3\_%'

In other words I am looking for records where the second character is the underscore literal character.

The code generated by the model designer looks like this:

    public virtual RiskAnalysis.responsesDataTable GetResponseGroupForAnalysis(int raid, string fieldid) {
    this.Adapter.SelectCommand = this.CommandCollection[2];
    this.Adapter.SelectCommand.Parameters[0].Value = ((int)(raid));
    if ((fieldid == null)) {
        throw new global::System.ArgumentNullException("fieldid");
    }
    else {
        this.Adapter.SelectCommand.Parameters[1].Value = ((string)(fieldid));
    }
    RiskAnalysis.responsesDataTable dataTable = new RiskAnalysis.responsesDataTable();
    this.Adapter.Fill(dataTable);
    return dataTable;
}

If I call this function like so:

string filter_string = @"3\_%";    
ResponsesAdapter.GetResponseGroupForAnalysis(10, filter_string);

the MySQL log reports the query to look like this:

SELECT     *
FROM         responses
WHERE     (ra_id = 10) AND (field_id LIKE '3\\_%')

In other words the I know I’m missing something blindingly obvious here, but how do I place MySQL’s escape backslash in the query without C# (un)helpfully escaping it?

Answer 1

OK, it seems (by experiment – happy to hear explanation or documentation link) that in MySQL (field_id LIKE '3\_%'); is equivalent to (field_id LIKE '3\\_%'); and both will find records where field_id starts with ‘3_’. Got myself well confused there – thanks Mahmoud and René for trying to understand what I was getting at!