概述
一、前言
关于什么是Dapper（详细入口），在此不做赘述；本文仅对Dapper在.Net Core中的使用作扼要说明，所陈代码以示例讲解为主，乃抛砖引玉，开发者可根据自身需要进行扩展和调整；其中如有疏漏之处，望不吝斧正。
不了解Dapper的朋友可以看这篇文章：ORM框架之Dapper简介和性能测试
二、Dapper环境搭建
当前以.Net Core WebAPI或MVC项目为例，框架版本为.NET 5.0，相关NuGet包引用如下：
Install-Package Dapper
Install-Package Dapper.Contrib
Install-Package Dapper.SqlBuilder
Install-Package System.Data.SqlClient
其中Dapper.Contrib和Dapper.SqlBuilder为Dapper的扩展，当然，Dapper的扩展还有如Dapper.Rainbow等其他包，根据自身需要引用，对相关引用作下说明：
- Dapper：不言而喻；
- Dapper.Contrib：可使用对象进行数据表的增删改查，免却SQL语句的编写；
- Dapper.SqlBuilder：可以方便动态构建SQL语句，如Join、SELECT、Where、OrderBy等等；
- System.Data.SqlClient：由于示例数据库为Sql Server，如MySql则引用MySql.Data；
对于Dapper.Contrib实体配置选项，以Product类为例，作扼要说明如下：
[Table("Product")]
public class Product
{
[Key]
public int Id { get; set; }
public string Name{ get; set; }
public string Description { get; set; }
public decimal Price { get; set; }
public DateTime CreateTime { get; set; }
}对于实体配置项，有如下几个主要项：
- Table：指定数据库表名，可忽略；
- Key：指定为自动增长主键；
- ExplicitKey：指定非自动增长主键，如guid；
- Computed：计算列属性，Insert、Update操作将忽略此列；
- Write：是否可写入，true/false，如[Write(false)]，false时Insert、Update操作将忽略此列，比如可扩展局部类作数据表额外查询字段使用；
对于数据表对象实体，可结合T4模板生成即可。
三、Dapper封装
关于Dapper数据访问，这里参考Github上的某示例（入口：https://github.com/EloreTec/UnitOfWorkWithDapper），作修改调整封装如下：
定义DapperDBContext类
public abstract class DapperDBContext : IContext
{
private IDbConnection _connection;
private IDbTransaction _transaction;
private int? _commandTimeout = null;
private readonly DapperDBContextOptions _options;
public bool IsTransactionStarted { get; private set; }
protected abstract IDbConnection CreateConnection(string connectionString);
protected DapperDBContext(IOptions<DapperDBContextOptions> optionsAccessor)
{
_options = optionsAccessor.Value;
_connection = CreateConnection(_options.Configuration);
_connection.Open();
DebugPrint("Connection started.");
}
#region Transaction
public void BeginTransaction()
{
if (IsTransactionStarted)
throw new InvalidOperationException("Transaction is already started.");
_transaction = _connection.BeginTransaction();
IsTransactionStarted = true;
DebugPrint("Transaction started.");
}
public void Commit()
{
if (!IsTransactionStarted)
throw new InvalidOperationException("No transaction started.");
_transaction.Commit();
_transaction = null;
IsTransactionStarted = false;
DebugPrint("Transaction committed.");
}
public void Rollback()
{
if (!IsTransactionStarted)
throw new InvalidOperationException("No transaction started.");
_transaction.Rollback();
_transaction.Dispose();
_transaction = null;
IsTransactionStarted = false;
DebugPrint("Transaction rollbacked and disposed.");
}
#endregion Transaction
#region Dapper.Contrib.Extensions
public async Task<T> GetAsync<T>(int id) where T : class, new()
{
return await _connection.GetAsync<T>(id, _transaction, _commandTimeout);
}
public async Task<T> GetAsync<T>(string id) where T : class, new()
{
return await _connection.GetAsync<T>(id, _transaction, _commandTimeout);
}
public async Task<IEnumerable<T>> GetAllAsync<T>() where T : class, new()
{
return await _connection.GetAllAsync<T>();
}
public long Insert<T>(T model) where T : class, new()
{
return _connection.Insert<T>(model, _transaction, _commandTimeout);
}
public async Task<int> InsertAsync<T>(T model) where T : class, new()
{
return await _connection.InsertAsync<T>(model, _transaction, _commandTimeout);
}
public bool Update<T>(T model) where T : class, new()
{
return _connection.Update<T>(model, _transaction, _commandTimeout);
}
public async Task<bool> UpdateAsync<T>(T model) where T : class, new()
{
return await _connection.UpdateAsync<T>(model, _transaction, _commandTimeout);
}
public async Task<Page<T>> PageAsync<T>(long pageIndex, long pageSize, string sql, object param = null)
{
DapperPage.BuildPageQueries((pageIndex - 1) * pageSize, pageSize, sql, out string sqlCount, out string sqlPage);
var result = new Page<T>
{
CurrentPage = pageIndex,
ItemsPerPage = pageSize,
TotalItems = await _connection.ExecuteScalarAsync<long>(sqlCount, param)
};
result.TotalPages = result.TotalItems / pageSize;
if ((result.TotalItems % pageSize) != 0)
result.TotalPages++;
result.Items = await _connection.QueryAsync<T>(sqlPage, param);
return result;
}
#endregion
#region Dapper Execute & Query
public int ExecuteScalar(string sql, object param = null, CommandType commandType = CommandType.Text)
{
return _connection.ExecuteScalar<int>(sql, param, _transaction, _commandTimeout, commandType);
}
public async Task<int> ExecuteScalarAsync(string sql, object param = null, CommandType commandType = CommandType.Text)
{
return await _connection.ExecuteScalarAsync<int>(sql, param, _transaction, _commandTimeout, commandType);
}
public int Execute(string sql, object param = null, CommandType commandType = CommandType.Text)
{
return _connection.Execute(sql, param, _transaction, _commandTimeout, commandType);
}
public async Task<int> ExecuteAsync(string sql, object param = null, CommandType commandType = CommandType.Text)
{
return await _connection.ExecuteAsync(sql, param, _transaction, _commandTimeout, commandType);
}
public IEnumerable<T> Query<T>(string sql, object param = null, CommandType commandType = CommandType.Text)
{
return _connection.Query<T>(sql, param, _transaction, true, _commandTimeout, commandType);
}
public async Task<IEnumerable<T>> QueryAsync<T>(string sql, object param = null, CommandType commandType = CommandType.Text)
{
return await _connection.QueryAsync<T>(sql, param, _transaction, _commandTimeout, commandType);
}
public T QueryFirstOrDefault<T>(string sql, object param = null, CommandType commandType = CommandType.Text)
{
return _connection.QueryFirstOrDefault<T>(sql, param, _transaction, _commandTimeout, commandType);
}
public async Task<T> QueryFirstOrDefaultAsync<T>(string sql, object param = null, CommandType commandType = CommandType.Text)
{
return await _connection.QueryFirstOrDefaultAsync<T>(sql, param, _transaction, _commandTimeout, commandType);
}
public IEnumerable<TReturn> Query<TFirst, TSecond, TReturn>(string sql, Func<TFirst, TSecond, TReturn> map, object param = null, string splitOn = "Id", CommandType commandType = CommandType.Text)
{
return _connection.Query(sql, map, param, _transaction, true, splitOn, _commandTimeout, commandType);
}
public async Task<IEnumerable<TReturn>> QueryAsync<TFirst, TSecond, TReturn>(string sql, Func<TFirst, TSecond, TReturn> map, object param = null, string splitOn = "Id", CommandType commandType = CommandType.Text)
{
return await _connection.QueryAsync(sql, map, param, _transaction, true, splitOn, _commandTimeout, commandType);
}
public async Task<SqlMapper.GridReader> QueryMultipleAsync(string sql, object param = null, CommandType commandType = CommandType.Text)
{
return await _connection.QueryMultipleAsync(sql, param, _transaction, _commandTimeout, commandType);
}
#endregion Dapper Execute & Query
public void Dispose()
{
if (IsTransactionStarted)
Rollback();
_connection.Close();
_connection.Dispose();
_connection = null;
DebugPrint("Connection closed and disposed.");
}
private void DebugPrint(string message)
{
#if DEBUG
Debug.Print(">>> UnitOfWorkWithDapper - Thread {0}: {1}", Thread.CurrentThread.ManagedThreadId, message);
#endif
}
}以上代码涵盖了Dapper访问数据库的基本操作，分同步和异步，其中大部分不作赘述，着重说下分页部分；
异步分页构建（PageAsync）
分页这里为方便调用，只需传入要查询的Sql语句（如：SELECT * FROM Table，必须带Order BY）、页索引、页大小即可；
至于具体如何构建的，这里参照某小型ORM工具PetaPoco，抽取相关代码如下，有兴趣的同学也可以自行改造：
public class Page<T>
{
/// <summary>
/// The current page number contained in this page of result set
/// </summary>
public long CurrentPage { get; set; }
/// <summary>
/// The total number of pages in the full result set
/// </summary>
public long TotalPages { get; set; }
/// <summary>
/// The total number of records in the full result set
/// </summary>
public long TotalItems { get; set; }
/// <summary>
/// The number of items per page
/// </summary>
public long ItemsPerPage { get; set; }
/// <summary>
/// The actual records on this page
/// </summary>
public IEnumerable<T> Items { get; set; }
//public List<T> Items { get; set; }
}
public class DapperPage
{
public static void BuildPageQueries(long skip, long take, string sql, out string sqlCount, out string sqlPage)
{
// Split the SQL
if (!PagingHelper.SplitSQL(sql, out PagingHelper.SQLParts parts))
throw new Exception("Unable to parse SQL statement for paged query");
sqlPage = BuildPageSql.BuildPageQuery(skip, take, parts);
sqlCount = parts.sqlCount;
}
}
static class BuildPageSql
{
public static string BuildPageQuery(long skip, long take, PagingHelper.SQLParts parts)
{
parts.sqlSelectRemoved = PagingHelper.rxOrderBy.Replace(parts.sqlSelectRemoved, "", 1);
if (PagingHelper.rxDistinct.IsMatch(parts.sqlSelectRemoved))
{
parts.sqlSelectRemoved = "peta_inner.* FROM (SELECT " + parts.sqlSelectRemoved + ") peta_inner";
}
var sqlPage = string.Format("SELECT * FROM (SELECT ROW_NUMBER() OVER ({0}) peta_rn, {1}) peta_paged WHERE peta_rn>{2} AND peta_rn<={3}",
parts.sqlOrderBy ?? "ORDER BY (SELECT NULL)", parts.sqlSelectRemoved, skip, skip + take);
//args = args.Concat(new object[] { skip, skip + take }).ToArray();
return sqlPage;
}
//SqlServer 2012及以上
public static string BuildPageQuery2(long skip, long take, PagingHelper.SQLParts parts)
{
parts.sqlSelectRemoved = PagingHelper.rxOrderBy.Replace(parts.sqlSelectRemoved, "", 1);
if (PagingHelper.rxDistinct.IsMatch(parts.sqlSelectRemoved))
{
parts.sqlSelectRemoved = "peta_inner.* FROM (SELECT " + parts.sqlSelectRemoved + ") peta_inner";
}
var sqlOrderBy = parts.sqlOrderBy ?? "ORDER BY (SELECT NULL)";
var sqlPage = $"SELECT {parts.sqlSelectRemoved} {sqlOrderBy} OFFSET {skip} ROWS FETCH NEXT {take} ROWS ONLY";
return sqlPage;
}
}
static class PagingHelper
{
public struct SQLParts
{
public string sql;
public string sqlCount;
public string sqlSelectRemoved;
public string sqlOrderBy;
}
public static bool SplitSQL(string sql, out SQLParts parts)
{
parts.sql = sql;
parts.sqlSelectRemoved = null;
parts.sqlCount = null;
parts.sqlOrderBy = null;
// Extract the columns from "SELECT <whatever> FROM"
var m = rxColumns.Match(sql);
if (!m.Success)
return false;
// Save column list and replace with COUNT(*)
Group g = m.Groups[1];
parts.sqlSelectRemoved = sql.Substring(g.Index);
if (rxDistinct.IsMatch(parts.sqlSelectRemoved))
parts.sqlCount = sql.Substring(0, g.Index) + "COUNT(" + m.Groups[1].ToString().Trim() + ") " + sql.Substring(g.Index + g.Length);
else
parts.sqlCount = sql.Substring(0, g.Index) + "COUNT(*) " + sql.Substring(g.Index + g.Length);
// Look for the last "ORDER BY <whatever>" clause not part of a ROW_NUMBER expression
m = rxOrderBy.Match(parts.sqlCount);
if (!m.Success)
{
parts.sqlOrderBy = null;
}
else
{
g = m.Groups[0];
parts.sqlOrderBy = g.ToString();
parts.sqlCount = parts.sqlCount.Substring(0, g.Index) + parts.sqlCount.Substring(g.Index + g.Length);
}
return true;
}
public static Regex rxColumns = new Regex(@"As*SELECTs+((?:((?>((?<depth>)|)(?<-depth>)|.?)*(?(depth)(?!)))|.)*?)(?<!,s+)bFROMb", RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.Singleline | RegexOptions.Compiled);
public static Regex rxOrderBy = new Regex(@"bORDERs+BYs+(?!.*?(?:)|s+)ASs)(?:((?>((?<depth>)|)(?<-depth>)|.?)*(?(depth)(?!)))|[w().])+(?:s+(?:ASC|DESC))?(?:s*,s*(?:((?>((?<depth>)|)(?<-depth>)|.?)*(?(depth)(?!)))|[w().])+(?:s+(?:ASC|DESC))?)*", RegexOptions.RightToLeft | RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.Singleline | RegexOptions.Compiled);
public static Regex rxDistinct = new Regex(@"ADISTINCTs", RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.Singleline | RegexOptions.Compiled);
}对于构建分页语句，分别示例BuildPageQuery和BuildPageQuery2，前者为通过ROW_NUMBER进行分页（针对SqlServer2005、2008），后者通过OFFSET、FETCH分页（针对SqlServer2012及以上版本），相关辅助操作类一览便知，如果使用MySql数据库，可酌情自行封装；
至于Where查询的进一步封装，有兴趣的也可兑Dapper lamada查询进行扩展。
定义工作单元与事务
public interface IUnitOfWork : IDisposable
{
void SaveChanges();
}
public interface IUnitOfWorkFactory
{
IUnitOfWork Create();
}
public class UnitOfWork : IUnitOfWork
{
private readonly IContext _context;
public UnitOfWork(IContext context)
{
_context = context;
_context.BeginTransaction();
}
public void SaveChanges()
{
if (!_context.IsTransactionStarted)
throw new InvalidOperationException("Transaction have already been commited or disposed.");
_context.Commit();
}
public void Dispose()
{
if (_context.IsTransactionStarted)
_context.Rollback();
}
}
public class DapperUnitOfWorkFactory : IUnitOfWorkFactory
{
private readonly DapperDBContext _context;
public DapperUnitOfWorkFactory(DapperDBContext context)
{
_context = context;
}
public IUnitOfWork Create()
{
return new UnitOfWork(_context);
}
}定义数据仓储
#region Product
public partial interface IProductRepository
{
Task<Product> GetAsync(int id);
Task<IEnumerable<Product>> GetAllAsync();
long Insert(Product model);
Task<int> InsertAsync(Product model);
bool Update(Product model);
Task<bool> UpdateAsync(Product model);
int Count(string where, object param = null);
Task<int> CountAsync(string where, object param = null);
bool Exists(string where, object param = null);
Task<bool> ExistsAsync(string where, object param = null);
Product FirstOrDefault(string where, object param = null);
Task<Product> FirstOrDefaultAsync(string where, object param = null);
T FirstOrDefault<T>(string sql, object param = null);
Task<T> FirstOrDefaultAsync<T>(string sql, object param = null);
IEnumerable<Product> Fetch(SqlBuilder where);
Task<IEnumerable<Product>> FetchAsync(SqlBuilder where);
IEnumerable<T> Fetch<T>(string sql, SqlBuilder where, bool orderBy = true);
Task<IEnumerable<T>> FetchAsync<T>(string sql, SqlBuilder where, bool orderBy = true);
Task<Page<Product>> PageAsync(long pageIndex, long pageSize, SqlBuilder builder);
Task<Page<T>> PageAsync<T>(string sql, long pageIndex, long pageSize, SqlBuilder builder);
Task<SqlMapper.GridReader> QueryMultipleAsync(string sql, object param = null);
}
public partial class ProductRepository : IProductRepository
{
private readonly DapperDBContext _context;
public ProductRepository(DapperDBContext context)
{
_context = context;
}
public async Task<Product> GetAsync(int id)
{
return await _context.GetAsync<Product>(id);
}
public async Task<IEnumerable<Product>> GetAllAsync()
{
return await _context.GetAllAsync<Product>();
}
public long Insert(Product model)
{
return _context.Insert<Product>(model);
}
public async Task<int> InsertAsync(Product model)
{
return await _context.InsertAsync<Product>(model);
}
public bool Update(Product model)
{
return _context.Update<Product>(model);
}
public async Task<bool> UpdateAsync(Product model)
{
return await _context.UpdateAsync<Product>(model);
}
public int Count(string where, object param = null)
{
string strSql = $"SELECT COUNT(1) FROM Product {where}";
return _context.ExecuteScalar(strSql, param);
}
public async Task<int> CountAsync(string where, object param = null)
{
string strSql = $"SELECT COUNT(1) FROM Product {where}";
return await _context.ExecuteScalarAsync(strSql, param);
}
public bool Exists(string where, object param = null)
{
string strSql = $"SELECT TOP 1 1 FROM Product {where}";
var count = _context.ExecuteScalar(strSql, param);
return count > 0;
}
public async Task<bool> ExistsAsync(string where, object param = null)
{
string strSql = $"SELECT TOP 1 1 FROM Product {where}";
var count = await _context.ExecuteScalarAsync(strSql, param);
return count > 0;
}
public Product FirstOrDefault(string where, object param = null)
{
string strSql = $"SELECT TOP 1 * FROM Product {where}";
return _context.QueryFirstOrDefault<Product>(strSql, param);
}
public async Task<Product> FirstOrDefaultAsync(string where, object param = null)
{
string strSql = $"SELECT TOP 1 * FROM Product {where}";
return await _context.QueryFirstOrDefaultAsync<Product>(strSql, param);
}
public T FirstOrDefault<T>(string sql, object param = null)
{
return _context.QueryFirstOrDefault<T>(sql, param);
}
public async Task<T> FirstOrDefaultAsync<T>(string sql, object param = null)
{
return await _context.QueryFirstOrDefaultAsync<T>(sql, param);
}
public IEnumerable<Product> Fetch(SqlBuilder where)
{
var strSql = where.AddTemplate(@"SELECT * FROM Product /**where**/ /**orderby**/");
return _context.Query<Product>(strSql.RawSql, strSql.Parameters);
}
public async Task<IEnumerable<Product>> FetchAsync(SqlBuilder where)
{
var strSql = where.AddTemplate(@"SELECT * FROM Product /**where**/ /**orderby**/");
return await _context.QueryAsync<Product>(strSql.RawSql, strSql.Parameters);
}
public IEnumerable<T> Fetch<T>(string sql, SqlBuilder where, bool orderBy = true)
{
var _sql = orderBy ? $"{sql} /**where**/ /**orderby**/" : $"{sql} /**where**/";
var strSql = where.AddTemplate(_sql);
return _context.Query<T>(strSql.RawSql, strSql.Parameters);
}
public async Task<IEnumerable<T>> FetchAsync<T>(string sql, SqlBuilder where, bool orderBy = true)
{
var _sql = orderBy ? $"{sql} /**where**/ /**orderby**/" : $"{sql} /**where**/";
var strSql = where.AddTemplate(_sql);
return await _context.QueryAsync<T>(strSql.RawSql, strSql.Parameters);
}
public async Task<Page<Product>> PageAsync(long pageIndex, long pageSize, SqlBuilder builder)
{
var strSql = "SELECT * FROM Product";
return await PageAsync<Product>(strSql, pageIndex, pageSize, builder);
}
public async Task<Page<T>> PageAsync<T>(string sql, long pageIndex, long pageSize, SqlBuilder builder)
{
var strSql = builder.AddTemplate($"{sql} /**where**/ /**orderby**/");
return await _context.PageAsync<T>(pageIndex, pageSize, strSql.RawSql, strSql.Parameters);
}
public async Task<SqlMapper.GridReader> QueryMultipleAsync(string sql, object param = null)
{
return await _context.QueryMultipleAsync(sql, param);
}
}
#endregion根据自身需要进行调整或扩展，一般借助T4模板生成
数据库连接
通过Ioptions模式读取配置文件appsettings中连接字符串
public class MyDBContext : DapperDBContext
{
public MyDBContext(IOptions<DapperDBContextOptions> optionsAccessor) : base(optionsAccessor)
{
}
protected override IDbConnection CreateConnection(string connectionString)
{
IDbConnection conn = new SqlConnection(connectionString);
return conn;
}
}四、Dapper使用
Startup.cs注入并读取数据库连接字符串
{
"SQLConnString": "Data Source=(local);Initial Catalog=database;Persist Security Info=True;User ID=sa;Password=123456;MultipleActiveResultSets=True;",
"Logging": {
"LogLevel": {
"Default": "Information",
"Microsoft": "Warning",
"Microsoft.Hosting.Lifetime": "Information"
}
},
"AllowedHosts": "*"
}
services.AddDapperDBContext<MyDBContext>(options =>
{
options.Configuration = Configuration["SQLConnString"];
});简单示例WebAPI或Net Core MVC下的调用示例：
public class ProductController : BaseController
{
private readonly IProductRepository _productRepository;
public ProductController(
IProductRepository productRepository
)
{
_productRepository = productRepository;
}
//商品列表
[HttpGet]
public async Task<IActionResult> ProductList(DateTime? startDate, DateTime? endDate, int id = 1, int productStatus = 0, string keyword = "")
{
var model = new ProductModels();
var builder = new Dapper.SqlBuilder();
builder.Where("ProductStatus!=@ProductStatus", new { ProductStatus = productStatus });
if (startDate.HasValue)
{
builder.Where("CreateTime>=@startDate", new { startDate = startDate.Value});
}
if (endDate.HasValue)
{
builder.Where("CreateTime<@endDate", new { endDate = endDate.Value.AddDays(1)});
}
if (!string.IsNullOrWhiteSpace(keyword))
{
builder.Where("Name LIKE @keyword", new { keyword = $"%{StringHelper.ReplaceSql(keyword)}%" });
}
builder.OrderBy("SortNum DESC,CreateTime DESC");
var list = await _productRepository.PageAsync(id, PageSize, builder);
model.ProductList = new PagedList<Product>(list.Items, id, PageSize, list.TotalItems);
if (Request.IsAjaxRequest())
return PartialView("_ProductList", model.ProductList);
return View(model);
}
//添加商品
[HttpPost]
public async Task<int> AddProduct(ProductModels model)
{
return await _productRepository.InsertAsync(model);
}
}
public partial interface IProductService
{
Task<bool> AddProduct(Product productInfo, List<ProductStock> skuList);
}
public class ProductService: IProductService
{
private readonly DapperDBContext _context;
private readonly IUnitOfWorkFactory _uowFactory;
public ProductService(DapperDBContext context, IUnitOfWorkFactory uowFactory)
{
_context = context;
_uowFactory = uowFactory;
}
/// <summary>
/// 添加商品
/// </summary>
/// <param name="productInfo"></param>
/// <param name="skuList"></param>
/// <returns></returns>
public async Task<bool> AddProduct(Product productInfo, List<ProductStock> skuList)
{
var result = false;
using (var uow = _uowFactory.Create())
{
//添加产品
await _context.InsertAsync(productInfo);
//添加Sku库存售价
//await _context.InsertAsync(skuList);
uow.SaveChanges();
result = true;
}
return result;
}
}以上所述是小编给大家介绍的.Net Core下使用Dapper的方法，希望对大家有所帮助。在此也非常感谢大家对靠谱客网站的支持！
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