Вроде все ошибки устранил. не запускал.

PARR.DAL/Services/Implementations/ApplicationService.cs

@@ -0,0 +1,30 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using PARR.DAL.Context;
+using PARR.DAL.Models;
+using PARR.DAL.Services.Abstracts;
+using PARR.DAL.Services.Interfaces;
+
+namespace PARR.DAL.Services.Implementations
+{
+    internal class ApplicationService : BaseService<Application>, IApplicationService
+    {
+        private readonly DataContext dataContext;
+        private readonly ILogger<ApplicationService> logger;
+
+        public ApplicationService(DataContext dataContext, ILogger<ApplicationService> logger) : base(logger)
+        {
+            this.dataContext = dataContext;
+            this.logger = logger;
+        }
+
+        protected override DbSet<Application> EntitySet => dataContext.Applications;
+
+        protected override DataContext EntitiContext => dataContext;
+
+        public async Task<Application?> GetByNameAsync(string appName)
+        {
+            return await EntitySet.FirstOrDefaultAsync(t => t.Name.ToLower() == appName.Trim().ToLower());
+        }
+    }
+}