Determining if an entity exists in a database via a stored procedure Here is a short and simple Ajax method that returns "True" or "False" if an entity exists in a database via a stored procedure that returns just "Y" or "N" (the details of this entity and database are not relevant to my question though).  

This is the first time I've used the C# using() statement, and was wondering if anyone would be kind enough to review this and give me feedback.

[WebMethod]
public string ValidateEntity(string EntityType, string EntityName)
{
    string connstr = (from c in Companys where c.Name.Equals(company, StringComparison.OrdinalIgnoreCase) select c.ConnectionString).FirstOrDefault();
    if (connstr == null) { return "False"; }
    using (SqlConnection conn = new SqlConnection(connstr))
    {
        using (SqlDataAdapter da = new SqlDataAdapter())
        {
            using (da.SelectCommand = new SqlCommand("ValidateEntity", conn))
            {
                da.SelectCommand.CommandType = CommandType.StoredProcedure;
                da.SelectCommand.Parameters.AddWithValue("@EntityType", EntityType);
                da.SelectCommand.Parameters.AddWithValue("@EntityName", EntityName);
                using(DataSet ds = new DataSet())
                {
                    da.Fill(ds, "result_name");
                    DataTable dt = ds.Tables["result_name"];
                    if ( dt.Rows.Count &gt; 0){
                        if (dt.Rows[0]["Valid"].ToString()=="Y") { return "True"; }
                    }                             
                }
            }
        }
    }
    return "False";
}
I may be pointing out the obvious here, but the ValidateEntity Method returns a string. I would expect it to return a Boolean. 
There are a number of one and two letter variable names. We've not been restricted in the size of names for many years now. It would be good to give them more descriptive names and we can take advantage of C#'s case sensitivity. 

da = adapter
ds = dataSet (but perhaps something even more meaningful)
dt = table or resultNames

If you return a bool instead of a string, you could directly return here instead of using an if statement. 

if (dt.Rows[0]["Valid"].ToString()=="Y") { return "True"; }



Becomes

return (dt.Rows[0]["Valid"].ToString() == "Y");