C#中.NET7.0Windows窗体应用通过EF访问新建数据库

目录

一、 操作步骤

二、编写EF模型和数据库上下文       

三、移植（Migrations）数据库

四、编写应用程序

五、生成效果

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        前文已经说过.NET Framework4.8 控制台应用通过EF访问已经建立的和新建的数据库。

        前文已经说过.NET 6.0 控制台应用通过EF访问已经建立的数据库。 

        本文想说的是，.NET 7.0 Windows窗体应用通过EF访问新建数据库，这里的数据据库要根据事先编写好的EF模型、和数据库上下文，经过一番操作，移植（Migrations）出来的。这个数据库在“工具、连接到数据库”是看不到这个数据库的连接的。【本文涉及道德方法同样适用于.NET 6.0 Windows窗体应用】

一、 操作步骤 新建VS.NET 7.0 Windows窗体应用；安装适合版本的EF程序包，7.0.14；编写EF模型和数据库上下文，文件录入格式是添加新的类；移植（Migrations）数据库，资源管理器里生成Migrations夹；编写应用程序文件Form1.cs；运行；

        步骤1和步骤2作者以前的文章都讲过，不再重复叙述。

二、编写EF模型和数据库上下文       

        添加→新建项目→类，复制粘贴以下全文，一定要保证所有.cs文件在同一片空间下（namespace）。

//编写EF实体模型和数据库上下文 using Microsoft.EntityFrameworkCore; namespace _10_15 { public class BloggingContext : DbContext { public DbSet<Blog>? Blogs { get; set; } public DbSet<Post>? Posts { get; set; } protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) { optionsBuilder.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=EFGetStarted.ConsoleApp.NewDb;Trusted_Connection=True;"); } } public class Blog { public int? BlogId { get; set; } public string? Url { get; set; } public List<Post>? Posts { get; set; } } public class Post { public int? PostId { get; set; } public string? Title { get; set; } public string? Content { get; set; } public int? BlogId { get; set; } public Blog? Blog { get; set; } } }

三、移植（Migrations）数据库 //移植并新建数据库 PM> Import-Module C:\Users\YCZN_MT\.nuget\packages\microsoft.entityframeworkcore.tools\7.0.14\tools\EntityFrameworkCore.psd1 模块“EntityFrameworkCore”中的某些导入命令的名称包含未批准的动词，这些动词可能导致这些命令名不易被发现。若要查找具有未批准的动词的命令，请使用 Verbose 参数再次运行 Import-Module 命令。有关批准的动词列表，请键入 Get-Verb。 PM> Get-Verb Verb Group ---- ----- Add Common Clear Common Close Common Copy Common Enter Common Exit Common Find Common Format Common Get Common Hide Common Join Common Lock Common Move Common New Common Open Common Optimize Common Pop Common Push Common Redo Common Remove Common Rename Common Reset Common Resize Common Search Common Select Common Set Common Show Common Skip Common Split Common Step Common Switch Common Undo Common Unlock Common Watch Common Backup Data Checkpoint Data Compare Data Compress Data Convert Data ConvertFrom Data ConvertTo Data Dismount Data Edit Data Expand Data Export Data Group Data Import Data Initialize Data Limit Data Merge Data Mount Data Out Data Publish Data Restore Data Save Data Sync Data Unpublish Data Update Data Approve Lifecycle Assert Lifecycle Complete Lifecycle Confirm Lifecycle Deny Lifecycle Disable Lifecycle Enable Lifecycle Install Lifecycle Invoke Lifecycle Register Lifecycle Request Lifecycle Restart Lifecycle Resume Lifecycle Start Lifecycle Stop Lifecycle Submit Lifecycle Suspend Lifecycle Uninstall Lifecycle Unregister Lifecycle Wait Lifecycle Debug Diagnostic Measure Diagnostic Ping Diagnostic Repair Diagnostic Resolve Diagnostic Test Diagnostic Trace Diagnostic Connect Communications Disconnect Communications Read Communications Receive Communications Send Communications Write Communications Block Security Grant Security Protect Security Revoke Security Unblock Security Unprotect Security Use Other PM> Add-Migration 位于命令管道位置 1 的 cmdlet Add-Migration 请为以下参数提供值: Name: MyMigration Build started... Build succeeded. To undo this action, use Remove-Migration. PM> Update-Database Build started... Build succeeded. Applying migration '20231115072504_MyMigration'. Failed executing DbCommand (3ms) [Parameters=[], CommandType='Text', CommandTimeout='30'] CREATE TABLE [Blogs] ( [BlogId] int NOT NULL IDENTITY, [Url] nvarchar(max) NOT NULL, CONSTRAINT [PK_Blogs] PRIMARY KEY ([BlogId]) ); Microsoft.Data.SqlClient.SqlException (0x80131904): There is already an object named 'Blogs' in the database. at Microsoft.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction) at Microsoft.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction) at Microsoft.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose) at Microsoft.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady) at Microsoft.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean isAsync, Int32 timeout, Boolean asyncWrite) at Microsoft.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, Boolean sendToPipe, Int32 timeout, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry, String methodName) at Microsoft.Data.SqlClient.SqlCommand.ExecuteNonQuery() at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteNonQuery(RelationalCommandParameterObject parameterObject) at Microsoft.EntityFrameworkCore.Migrations.MigrationCommand.ExecuteNonQuery(IRelationalConnection connection, IReadOnlyDictionary`2 parameterValues) at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationCommandExecutor.ExecuteNonQuery(IEnumerable`1 migrationCommands, IRelationalConnection connection) at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.Migrate(String targetMigration) at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.UpdateDatabase(String targetMigration, String connectionString, String contextType) at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabaseImpl(String targetMigration, String connectionString, String contextType) at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabase.<>c__DisplayClass0_0.<.ctor>b__0() at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action) ClientConnectionId:9c23d064-4612-470a-873c-665d7d583836 Error Number:2714,State:6,Class:16 There is already an object named 'Blogs' in the database. PM>

        我的电脑中在其他项目中已经移植生成过同样的数据库，因此在数据库更新时提示并警告，忽略就好了，不影响本项目的调试和运行的。

四、编写应用程序 // .NET 7.0窗体应用访问新建数据库 // 对数据库进行追加记录、删除记录操作 namespace _10_15 { public partial class Form1 : Form { public Form1() { InitializeComponent(); } /// <summary> /// 初始化Form1 /// 初始化表格，显示数据表 /// </summary> private void Form1_Load(object sender, EventArgs e) { button1.Text = "追加"; button2.Text = "删除"; label1.Text = "追加的Url："; label2.Text = "删除的ID："; button1.Size = new Size(40, 23); button2.Size = new Size(40, 23); dataGridView1.AllowUserToAddRows = false; dataGridView1.AllowUserToDeleteRows = false; dataGridView1.AllowUserToResizeColumns = false; dataGridView1.AllowUserToResizeRows = false; dataGridView1.RowHeadersVisible = false; dataGridView1.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.AllCells; using var db = new BloggingContext(); dataGridView1.DataSource = db.Blogs?.ToList(); } /// <summary> /// 追加Add() /// 无论ID是否连续，都在数据库末尾追加新纪录 /// </summary> private void Button1_Click(object sender, EventArgs e) { using var db = new BloggingContext(); if (textBox1.Text != "") { db.Blogs?.Add(new Blog { Url = textBox1.Text.Trim().ToString() }); //追加记录 db.SaveChanges(); dataGridView1.DataSource = db.Blogs?.ToList(); } else { db.Blogs?.Add(new Blog { Url = "http:// .hao123 /" }); //追加记录 db.SaveChanges(); dataGridView1.DataSource = db.Blogs?.ToList(); } } /// <summary> /// 删除Remove() /// </summary> private void Button2_Click(object sender, EventArgs e) { using var db = new BloggingContext(); db.Blogs?.Remove(new Blog { BlogId = Convert.ToInt32(textBox2.Text.Trim()) }); //删除记录按ID db.SaveChanges(); dataGridView1.DataSource = db.Blogs?.ToList(); } } } 五、生成效果

        追加：http://news.sina /

        删除：ID=3的记录