注：如果你使用Dapper一段時間了，這篇你可以跳過去了。

　　在第十二篇中，我們聊過官方的ORM——EntityFramework，它可以把SQL細節都隱藏，這對於一些標準化的關係資料庫專案非常便捷。今天，介紹另外一個流行的ORM——Dapper，Dapper是通過擴充套件IDbConnection方法來達到對資料的處理的，特點是靈活，高效。

　　還是通過專案看看Dapper的使用。首先安裝兩個NuGet包，我們還是使用之前的Exam專案的表來說明Dapper使用，庫是SQL Server。

　　安裝Dapper和SqlClient：

Install-Package Dapper

Install-Package Microsoft.Data.SqlClient

　　下面是對Question進行增刪改查

using Dapper;
using Microsoft.Data.SqlClient;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddScoped<IQuestionService, QuestionService>();
var app = builder.Build();

app.MapPost("/question", async (IQuestionService questionService, QuestionModel question) =>
{
    return await questionService.AddQuestionAsync(question);
});

app.MapPut("/question", async (IQuestionService questionService, QuestionModel question) =>
{
    return await questionService.ModifyQuestionAsync(question);
});

app.MapGet("/question/{id}", async (IQuestionService questionService, int id) =>
{
    return await questionService.GetQuestionAsync(id);

});

app.MapDelete("/question/{id}", async (IQuestionService questionService, int id) =>
{
    return await questionService.DeleteQuestionAsync(id);
});

app.Run();

public interface IQuestionService
{
    Task<QuestionModel> GetQuestionAsync(int id);
    Task<bool> AddQuestionAsync(QuestionModel question);
    Task<bool> DeleteQuestionAsync(int id);
    Task<bool> ModifyQuestionAsync(QuestionModel question);
}
public class QuestionService : IQuestionService
{
    private readonly SqlConnection _connection;
    public QuestionService(IConfiguration configuration)
    {
        var connectionString = configuration.GetConnectionString("ExamDatabase");
        _connection = new SqlConnection(connectionString);

    }
    public async Task<bool> AddQuestionAsync(QuestionModel question)
    {
        var sql = @"INSERT INTO [Questions]
           ([Question]
           ,[Score]
           ,[QuestionTypeID]
           ,[SujectTypeID])
     VALUES
           (@Question
           ,@Score
           ,@QuestionTypeID
           ,@SujectTypeID)";
        return (await _connection.ExecuteAsync(sql, question)) > 0;
    }

    public async Task<bool> DeleteQuestionAsync(int id)
    {
        var sql = @"delete from questions where id=@id";
        return (await _connection.ExecuteAsync(sql, new { id })) > 0;
    }

    public async Task<QuestionModel> GetQuestionAsync(int id)
    {
        var sql = @"select * from questions where id=@id";
        return await _connection.QuerySingleAsync<QuestionModel>(sql, new { id });
    }

    public async Task<bool> ModifyQuestionAsync(QuestionModel question)
    {
        var sql = @"UPDATE [dbo].[Questions]
   SET [Question] = @Question
      ,[Score] = @Score
      ,[QuestionTypeID] = @QuestionTypeID
      ,[SujectTypeID] = @SujectTypeID
 WHERE ID=@ID";
        return (await _connection.ExecuteAsync(sql, question)) > 0;
    }
}
 

　　通過上面事例，可以看到Dapper通過擴充套件IDbConnection的擴充套件方法來提供功能，基本上查詢用Query<T>(sql,Param,...)，增刪改用Execute(sql,T,...)，Dapper的方便之處是T全部是自運對映到sql中的引數的，這樣就能做到sql我們可以靈活且更高效語法編寫，引數可以方便的進出sql，達到一個平衡點。如下圖示：

 　　關於更豐富多彩的Dapper使用，詳見Github倉庫說明文件：https://github.com/DapperLib/Dapper