Initial Commit ...

Providers/XGuidKeyGenerator.cs

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+using System;
+using System.Threading.Tasks;
+using xCommons.Extensions;
+using xDataService.Interfaces;
+using xModels.Base;
+
+namespace xDataService.Providers {
+    public class XGuidKeyGenerator<TEntity> : IXKeyGenerator<TEntity, Guid>
+        where TEntity : XBaseEntity<Guid> {
+            private readonly IXSequentialGuid sequentialGuid;
+
+            public XGuidKeyGenerator (
+                IXSequentialGuid sequentialGuid = null
+            ) {
+                this.sequentialGuid = sequentialGuid;
+            }
+
+            public async Task<Guid> GenerateKey (
+                IXBaseRepository<TEntity, Guid> repository
+            ) {
+                //
+                await Task.CompletedTask;
+
+                //
+                // Check if provided SequentialGuid ...
+                if (sequentialGuid.IsNull ()) {
+                    return Guid.NewGuid ();
+                } else {
+                    return sequentialGuid.Next ();
+                }
+            }
+
+            public bool IsEmpty (Guid id) {
+                //
+                var result = id.IsNull () || id.IsDefaultGuid ();
+
+                //
+                return result;
+            }
+        }
+}

Providers/XIntKeyGenerator.cs

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+using System.Linq;
+using System.Threading.Tasks;
+using xCommons.Extensions;
+using xDataService.Extensions;
+using xDataService.Interfaces;
+using xModels.Base;
+
+namespace xDataService.Providers {
+    public class XIntKeyGenerator<TEntity> : IXKeyGenerator<TEntity, int>
+        where TEntity : XBaseEntity<int> {
+            public async Task<int> GenerateKey (IXBaseRepository<TEntity, int> repository) {
+                //
+                var items = (await repository.GetAllAsync ())
+                    .OrderByDescending (nameof (XBaseEntity<int>.Id));
+                var last = items
+                    .FirstOrDefault ();
+
+                //
+                var result = last.IsNull () ? 1 : last.Id + 1;
+
+                //
+                return result;
+            }
+
+            public bool IsEmpty (int id) {
+                //
+                var result = id <= 0;
+
+                //
+                return result;
+            }
+        }
+}

Providers/XSequentialGuid.cs

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+using System;
+using xDataService.Interfaces;
+
+namespace xDataService.Helpers {
+    /// <summary>
+    /// this service provide Sequential GUID mechanism for Entity Ids ...
+    /// </summary>
+    public class XSequentialGuid : IXSequentialGuid {
+        private static int[] sqlOrderMap = null;
+        private static int[] SQLORDERMAP {
+            get {
+                if (sqlOrderMap == null) {
+                    sqlOrderMap = new int[16] {
+                    3,
+                    2,
+                    1,
+                    0,
+                    5,
+                    4,
+                    7,
+                    6,
+                    9,
+                    8,
+                    15,
+                    14,
+                    13,
+                    12,
+                    11,
+                    10
+                    };
+                    // 3 - the least significant byte in Guid ByteArray [for SQL Server ORDER BY clause]
+                    // 10 - the most significant byte in Guid ByteArray [for SQL Server ORDERY BY clause]
+                }
+                return sqlOrderMap;
+            }
+        }
+
+        private Guid currentGuid;
+
+        public XSequentialGuid () {
+            currentGuid = Guid.NewGuid ();
+        }
+
+        public Guid GetCurrentGuid () {
+            return currentGuid;
+        }
+
+        public Guid Next () {
+            byte[] bytes = currentGuid.ToByteArray ();
+            for (int mapIndex = 0; mapIndex < 16; mapIndex++) {
+                int bytesIndex = SQLORDERMAP[mapIndex];
+                bytes[bytesIndex]++;
+                if (bytes[bytesIndex] != 0) {
+                    break; // No need to increment more significant bytes
+                }
+            }
+            currentGuid = new Guid (bytes);
+            return currentGuid;
+        }
+    }
+}

Providers/XStringKeyGenerator.cs

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+using System;
+using System.Threading.Tasks;
+using xCommons.Extensions;
+using xDataService.Interfaces;
+using xModels.Base;
+
+namespace xDataService.Providers {
+    public class XStringKeyGenerator : IXKeyGenerator<XBaseEntity<string>, string> {
+        private readonly IXSequentialGuid sequentialGuid;
+
+        public XStringKeyGenerator (IXSequentialGuid sequentialGuid = null) {
+            this.sequentialGuid = sequentialGuid;
+        }
+
+        public async Task<string> GenerateKey (IXBaseRepository<XBaseEntity<string>, string> repository) {
+            //
+            await Task.CompletedTask;
+
+            //
+            if (sequentialGuid.IsNull ()) {
+                return Guid.NewGuid ().ToString ();
+            } else {
+                return sequentialGuid.Next ().ToString ();
+            }
+        }
+
+        public bool IsEmpty (string id) {
+            return id.IsNullOrEmpty ();
+        }
+    }
+}