OleDbCommand objCmdSelect = new OleDbCommand("SELECT * FROM [List1$A1:A1]", objConn);
        object hodnota = objCmdSelect.ExecuteScalar();
        this.Label1.Text = hodnota.ToString();

Object reference not set to an instance of an object.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.