Comparing date field in sql with a date from c#label

First of all having a Label that displays a date is not such a good idea (unless it is actually bound to a DateTime Object). If that is the case you should really use your DateTime Object in a PARAMETERIZED QUERY!!!
Parameterized queries keep your calls to the database clean and safe (no SQL injection!) :)
The code should look something like this:

DateTime dt = DateTime.Today;
String query = "select name from vacseat where dt = @dt";
DbCommand cmd = new DbCommand(query, connectionObject); // Probably an SqlCommand or something.
cmd.Parameters.AddWithValue("@dt", dt); // Replaces @dt in your query with an actual date!
// Etc...

This should do the trick :)
For more info on Command Object see this MSDN page[^].
Good luck! :)

First of all, the date format in SQL Server(hoping this is your database tech.) and the date format in .NET has to match in there format. Usually the format you get in SQL Server is not directly match. Unless you convert it helper SQL function. One of SQL Server function that helps for such kind of case is Convert [^]function.So you query will look like

string query = "select name from vacseat where CONVERT(VARCHAR(10),dt,105)= '"+lblDate.Text+"'"; // Will format native SQL date time value to dd-mm-yyyy format

In addition to this what Naerling has suggest about SQL Injection is quite helpful for database safety.

Home this will help you well.