添加项目文件。

TechHelper.Server/Context/Configuration/AssignmentAttachmentConfiguration.cs

@@ -0,0 +1,48 @@
+using Entities.Contracts;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+using Microsoft.EntityFrameworkCore;
+
+namespace TechHelper.Context.Configuration
+{
+	public class AssignmentAttachmentConfiguration : IEntityTypeConfiguration<AssignmentAttachment>
+	{
+		public void Configure(EntityTypeBuilder<AssignmentAttachment> builder)
+		{
+			builder.ToTable("assignment_attachments");
+
+			builder.HasKey(aa => aa.Id);
+
+			builder.Property(aa => aa.Id)
+				.HasColumnName("id");
+
+			builder.Property(aa => aa.AssignmentId)
+				.HasColumnName("assignment_id")
+				.IsRequired();
+
+			builder.Property(aa => aa.FilePath)
+				.HasColumnName("file_path")
+				.IsRequired()
+				.HasMaxLength(255);
+
+			builder.Property(aa => aa.FileName)
+				.HasColumnName("file_name")
+				.IsRequired()
+				.HasMaxLength(255);
+
+			builder.Property(aa => aa.UploadedAt)
+				.HasColumnName("uploaded_at")
+				.ValueGeneratedOnAdd(); // Set value on creation
+
+			builder.Property(aa => aa.IsDeleted)
+				.HasColumnName("deleted")
+				.HasDefaultValue(false);
+
+			// Configure the relationship explicitly
+			builder.HasOne(aa => aa.Assignment) // An AssignmentAttachment has one Assignment
+				   .WithMany(a => a.AssignmentAttachments) // An Assignment has many AssignmentAttachments (assuming 'Attachments' collection in Assignment)
+				   .HasForeignKey(aa => aa.AssignmentId) // The foreign key is AssignmentAttachment.AssignmentId
+				   .IsRequired() // It's a required relationship based on your [Required] attribute
+				   .OnDelete(DeleteBehavior.Cascade); // If an Assignment is deleted, its attachments should also be deleted
+		}
+	}
+}