diff --git a/SPiluSZharuProject/SPiluSZharuContracts/DataModels/PostDataModel.cs b/SPiluSZharuProject/SPiluSZharuContracts/DataModels/PostDataModel.cs
new file mode 100644
index 0000000..e8042e0
--- /dev/null
+++ b/SPiluSZharuProject/SPiluSZharuContracts/DataModels/PostDataModel.cs
@@ -0,0 +1,47 @@
+using SPiluSZharuContracts.Enums;
+using SPiluSZharuContracts.Exceptions;
+using SPiluSZharuContracts.Extensions;
+using SPiluSZharuContracts.Infrastructure;
+
+namespace SPiluSZharuContracts.DataModels;
+
+internal class PostDataModel(string id, string postId, string postName, PostType postType, double salary, bool isActual, DateTime changeDate) : IValidation
+{
+    public string Id { get; private set; } = id;
+
+    public string PostId { get; private set; } = postId;
+
+    public string PostName { get; private set; } = postName;
+
+    public PostType PostType { get; private set; } = postType;
+
+    public double Salary { get; private set; } = salary;
+
+    public bool IsActual { get; private set; } = isActual;
+
+    public DateTime ChangeDate { get; private set; } = changeDate;
+
+    public void Validate()
+    {
+        if (Id.IsEmpty())
+            throw new ValidationException("Field Id is empty");
+
+        if (!Id.IsGuid())
+            throw new ValidationException("The value in the field Id is not a unique identifier");
+
+        if (PostId.IsEmpty())
+            throw new ValidationException("Field PostId is empty");
+
+        if (!PostId.IsGuid())
+            throw new ValidationException("The value in the field PostId is not a unique identifier");
+
+        if (PostName.IsEmpty())
+            throw new ValidationException("Field PostName is empty");
+
+        if (PostType == PostType.None)
+            throw new ValidationException("Field PostType is empty");
+
+        if (Salary <= 0)
+            throw new ValidationException("Field Salary is empty");
+    }
+}
diff --git a/SPiluSZharuProject/SPiluSZharuContracts/DataModels/ProductDataModel.cs b/SPiluSZharuProject/SPiluSZharuContracts/DataModels/ProductDataModel.cs
new file mode 100644
index 0000000..38a7b28
--- /dev/null
+++ b/SPiluSZharuProject/SPiluSZharuContracts/DataModels/ProductDataModel.cs
@@ -0,0 +1,37 @@
+using SPiluSZharuContracts.Enums;
+using SPiluSZharuContracts.Exceptions;
+using SPiluSZharuContracts.Extensions;
+using SPiluSZharuContracts.Infrastructure;
+
+namespace SPiluSZharuContracts.DataModels;
+
+public class ProductDataModel(string id, string productName, ProductType productType, double price, bool isDeleted) : IValidation
+{
+    public string Id { get; private set; } = id;
+
+    public string ProductName { get; private set; } = productName;
+
+    public ProductType ProductType { get; private set; } = productType;
+
+    public double Price { get; private set; } = price;
+
+    public bool IsDeleted { get; private set; } = isDeleted;
+
+    public void Validate()
+    {
+        if (Id.IsEmpty())
+            throw new ValidationException("Field Id is empty");
+
+        if (!Id.IsGuid())
+            throw new ValidationException("The value in the field Id is not a unique identifier");
+
+        if (ProductName.IsEmpty())
+            throw new ValidationException("Field ProductName is empty");
+
+        if (ProductType == ProductType.None)
+            throw new ValidationException("Field ProductType is empty");
+
+        if (Price <= 0)
+            throw new ValidationException("Field Price is less than or equal to 0");
+    }
+}
diff --git a/SPiluSZharuProject/SPiluSZharuContracts/DataModels/ProductHistoryDataModel.cs b/SPiluSZharuProject/SPiluSZharuContracts/DataModels/ProductHistoryDataModel.cs
new file mode 100644
index 0000000..a4a92bc
--- /dev/null
+++ b/SPiluSZharuProject/SPiluSZharuContracts/DataModels/ProductHistoryDataModel.cs
@@ -0,0 +1,26 @@
+using SPiluSZharuContracts.Exceptions;
+using SPiluSZharuContracts.Extensions;
+using SPiluSZharuContracts.Infrastructure;
+
+namespace SPiluSZharuContracts.DataModels;
+
+public class ProductHistoryDataModel(string productId, double oldPrice) : IValidation
+{
+    public string ProductId { get; private set; } = productId;
+
+    public double OldPrice { get; private set; } = oldPrice;
+
+    public DateTime ChangeDate { get; private set; } = DateTime.UtcNow;
+
+    public void Validate()
+    {
+        if (ProductId.IsEmpty())
+            throw new ValidationException("Field ProductId is empty");
+
+        if (!ProductId.IsGuid())
+            throw new ValidationException("The value in the field ProductId is not a unique identifier");
+
+        if (OldPrice <= 0)
+            throw new ValidationException("Field OldPrice is less than or equal to 0");
+    }
+}
diff --git a/SPiluSZharuProject/SPiluSZharuContracts/DataModels/RestaurantDataModel.cs b/SPiluSZharuProject/SPiluSZharuContracts/DataModels/RestaurantDataModel.cs
new file mode 100644
index 0000000..45e8214
--- /dev/null
+++ b/SPiluSZharuProject/SPiluSZharuContracts/DataModels/RestaurantDataModel.cs
@@ -0,0 +1,26 @@
+using SPiluSZharuContracts.Exceptions;
+using SPiluSZharuContracts.Extensions;
+using SPiluSZharuContracts.Infrastructure;
+
+namespace SPiluSZharuContracts.DataModels;
+
+public class RestaurantDataModel(string id, string restaurantName, string? prevRestaurantName, string? prevPrevRestaurantName) : IValidation
+{
+    public string Id { get; private set; } = id;
+
+    public string RestaurantName { get; private set; } = restaurantName;
+
+    public string? PrevRestaurantName { get; private set; } = prevRestaurantName;
+
+    public string? PrevPrevRestaurantName { get; private set; } = prevPrevRestaurantName;
+
+    public void Validate()
+    {
+        if (Id.IsEmpty())
+            throw new ValidationException("Field Id is empty");
+        if (!Id.IsGuid())
+            throw new ValidationException("The value in the field Id is not a unique identifier");
+        if (RestaurantName.IsEmpty())
+            throw new ValidationException("Field RestaurantName is empty");
+    }
+}
diff --git a/SPiluSZharuProject/SPiluSZharuContracts/DataModels/SaleDataModel.cs b/SPiluSZharuProject/SPiluSZharuContracts/DataModels/SaleDataModel.cs
new file mode 100644
index 0000000..c39f338
--- /dev/null
+++ b/SPiluSZharuProject/SPiluSZharuContracts/DataModels/SaleDataModel.cs
@@ -0,0 +1,46 @@
+using SPiluSZharuContracts.Exceptions;
+using SPiluSZharuContracts.Extensions;
+using SPiluSZharuContracts.Infrastructure;
+
+namespace SPiluSZharuContracts.DataModels;
+
+public class SaleDataModel(string id, string workerId, string? restaurantId, double sum, bool isCancel, List<SaleProductDataModel> products) : IValidation
+{
+    public string Id { get; private set; } = id;
+
+    public string WorkerId { get; private set; } = workerId;
+
+    public string? RestaurantId { get; private set; } = restaurantId;
+
+    public DateTime SaleDate { get; private set; } = DateTime.UtcNow;
+
+    public double Sum { get; private set; } = sum;
+
+    public bool IsCancel { get; private set; } = isCancel;
+
+    public List<SaleProductDataModel> Products { get; private set; } = products;
+
+    public void Validate()
+    {
+        if (Id.IsEmpty())
+            throw new ValidationException("Field Id is empty");
+
+        if (!Id.IsGuid())
+            throw new ValidationException("The value in the field Id is not a unique identifier");
+
+        if (WorkerId.IsEmpty())
+            throw new ValidationException("Field WorkerId is empty");
+
+        if (!WorkerId.IsGuid())
+            throw new ValidationException("The value in the field WorkerId is not a unique identifier");
+
+        if (!RestaurantId?.IsGuid() ?? !RestaurantId?.IsEmpty() ?? false)
+            throw new ValidationException("The value in the field RestaurantId is not a unique identifier");
+
+        if (Sum <= 0)
+            throw new ValidationException("Field Sum is less than or equal to 0");
+
+        if ((Products?.Count ?? 0) == 0)
+            throw new ValidationException("The sale must include products");
+    }
+}
diff --git a/SPiluSZharuProject/SPiluSZharuContracts/DataModels/SaleProductDataModel.cs b/SPiluSZharuProject/SPiluSZharuContracts/DataModels/SaleProductDataModel.cs
new file mode 100644
index 0000000..3142f33
--- /dev/null
+++ b/SPiluSZharuProject/SPiluSZharuContracts/DataModels/SaleProductDataModel.cs
@@ -0,0 +1,32 @@
+using SPiluSZharuContracts.Exceptions;
+using SPiluSZharuContracts.Extensions;
+using SPiluSZharuContracts.Infrastructure;
+
+namespace SPiluSZharuContracts.DataModels;
+
+public class SaleProductDataModel(string saleId, string productId, int count) : IValidation
+{
+    public string SaleId { get; private set; } = saleId;
+
+    public string ProductId { get; private set; } = productId;
+
+    public int Count { get; private set; } = count;
+
+    public void Validate()
+    {
+        if (SaleId.IsEmpty())
+            throw new ValidationException("Field SaleId is empty");
+
+        if (!SaleId.IsGuid())
+            throw new ValidationException("The value in the field SaleId is not a unique identifier");
+
+        if (ProductId.IsEmpty())
+            throw new ValidationException("Field ProductId is empty");
+
+        if (!ProductId.IsGuid())
+            throw new ValidationException("The value in the field ProductId is not a unique identifier");
+
+        if (Count <= 0)
+            throw new ValidationException("Field Count is less than or equal to 0");
+    }
+}
diff --git a/SPiluSZharuProject/SPiluSZharuContracts/DataModels/WorkerDataModel.cs b/SPiluSZharuProject/SPiluSZharuContracts/DataModels/WorkerDataModel.cs
new file mode 100644
index 0000000..0fb11fc
--- /dev/null
+++ b/SPiluSZharuProject/SPiluSZharuContracts/DataModels/WorkerDataModel.cs
@@ -0,0 +1,47 @@
+using SPiluSZharuContracts.Exceptions;
+using SPiluSZharuContracts.Extensions;
+using SPiluSZharuContracts.Infrastructure;
+
+namespace SPiluSZharuContracts.DataModels;
+
+public class WorkerDataModel(string id, string fio, string postId, DateTime birthDate, DateTime employmentDate, bool isDeleted) : IValidation
+{
+    public string Id { get; private set; } = id;
+
+    public string FIO { get; private set; } = fio;
+
+    public string PostId { get; private set; } = postId;
+
+    public DateTime BirthDate { get; private set; } = birthDate;
+
+    public DateTime EmploymentDate { get; private set; } = employmentDate;
+
+    public bool IsDeleted { get; private set; } = isDeleted;
+
+    public void Validate()
+    {
+        if (Id.IsEmpty())
+            throw new ValidationException("Field Id is empty");
+
+        if (!Id.IsGuid())
+            throw new ValidationException("The value in the field Id is not a unique identifier");
+
+        if (FIO.IsEmpty())
+            throw new ValidationException("Field FIO is empty");
+
+        if (PostId.IsEmpty())
+            throw new ValidationException("Field PostId is empty");
+
+        if (!PostId.IsGuid())
+            throw new ValidationException("The value in the field PostId is not a unique identifier");
+
+        if (BirthDate.Date > DateTime.Now.AddYears(-16).Date)
+            throw new ValidationException($"Minors cannot be hired (BirthDate = {BirthDate.ToShortDateString()})");
+
+        if (EmploymentDate.Date < BirthDate.Date)
+            throw new ValidationException("The date of employment cannot be less than the date of birth");
+
+        if ((EmploymentDate - BirthDate).TotalDays / 365 < 16) // EmploymentDate.Year - BirthDate.Year
+            throw new ValidationException($"Minors cannot be hired (EmploymentDate - {EmploymentDate.ToShortDateString()}, BirthDate - {BirthDate.ToShortDateString()})");
+    }
+}
diff --git a/SPiluSZharuProject/SPiluSZharuContracts/Enums/PostType.cs b/SPiluSZharuProject/SPiluSZharuContracts/Enums/PostType.cs
new file mode 100644
index 0000000..8a2145a
--- /dev/null
+++ b/SPiluSZharuProject/SPiluSZharuContracts/Enums/PostType.cs
@@ -0,0 +1,9 @@
+namespace SPiluSZharuContracts.Enums;
+
+public enum PostType
+{
+    None = 0,
+    Operator = 1,
+    OrderPicker = 2,
+    DeliveryMan = 3
+}
diff --git a/SPiluSZharuProject/SPiluSZharuContracts/Enums/ProductType.cs b/SPiluSZharuProject/SPiluSZharuContracts/Enums/ProductType.cs
new file mode 100644
index 0000000..924b03c
--- /dev/null
+++ b/SPiluSZharuProject/SPiluSZharuContracts/Enums/ProductType.cs
@@ -0,0 +1,9 @@
+namespace SPiluSZharuContracts.Enums;
+
+public enum ProductType
+{
+    None = 0,
+    Pizza = 1,
+    Burgers = 2,
+    Drinks = 3
+}
diff --git a/SPiluSZharuProject/SPiluSZharuContracts/Exceptions/ValidationException.cs b/SPiluSZharuProject/SPiluSZharuContracts/Exceptions/ValidationException.cs
new file mode 100644
index 0000000..758b754
--- /dev/null
+++ b/SPiluSZharuProject/SPiluSZharuContracts/Exceptions/ValidationException.cs
@@ -0,0 +1,5 @@
+namespace SPiluSZharuContracts.Exceptions;
+
+public class ValidationException(string message) : Exception(message)
+{
+}
diff --git a/SPiluSZharuProject/SPiluSZharuContracts/Extensions/StringExtensions.cs b/SPiluSZharuProject/SPiluSZharuContracts/Extensions/StringExtensions.cs
new file mode 100644
index 0000000..aa2298e
--- /dev/null
+++ b/SPiluSZharuProject/SPiluSZharuContracts/Extensions/StringExtensions.cs
@@ -0,0 +1,14 @@
+namespace SPiluSZharuContracts.Extensions;
+
+public static class StringExtensions
+{
+    public static bool IsEmpty(this string str)
+    {
+        return string.IsNullOrWhiteSpace(str);
+    }
+
+    public static bool IsGuid(this string str)
+    {
+        return Guid.TryParse(str, out _);
+    }
+}
diff --git a/SPiluSZharuProject/SPiluSZharuContracts/Infrastructure/IValidation.cs b/SPiluSZharuProject/SPiluSZharuContracts/Infrastructure/IValidation.cs
new file mode 100644
index 0000000..917889b
--- /dev/null
+++ b/SPiluSZharuProject/SPiluSZharuContracts/Infrastructure/IValidation.cs
@@ -0,0 +1,6 @@
+namespace SPiluSZharuContracts.Infrastructure;
+
+public interface IValidation
+{
+    void Validate();
+}