看一下它的基本参数和方法声明：
public static GridReader QueryMultiple(this IDbConnection cnn, string sql, object param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null);这个方法返回一个GridReader，通过Read方法获取需要的数据。
5. 不只是查询Dapper当然不只有查询这一项功能，Dapper支持使用存储过程、insert、update、delete等其他的SQL语句进行操作数据库。使用方式：
string sql = "Invoice_Insert"; using (var connection = My.ConnectionFactory()) { var affectedRows = connection.Execute(sql, new {Kind = InvoiceKind.WebInvoice, Code = "Single_Insert_1"}, commandType: CommandType.StoredProcedure); var affectedRows2 = connection.Execute(sql, new[] { new {Kind = InvoiceKind.WebInvoice, Code = "Many_Insert_1"}, new {Kind = InvoiceKind.WebInvoice, Code = "Many_Insert_2"}, new {Kind = InvoiceKind.StoreInvoice, Code = "Many_Insert_3"} }, commandType: CommandType.StoredProcedure ); }示例就是使用存储过程的例子。
string sql = "INSERT INTO Customers (CustomerName) Values (@CustomerName);"; using (var connection = new SqlConnection(FiddleHelper.GetConnectionStringSqlServerW3Schools())) { var affectedRows = connection.Execute(sql, new {CustomerName = "Mark"}); Console.WriteLine(affectedRows); var customer = connection.Query<Customer>("Select * FROM CUSTOMERS WHERE CustomerName = 'Mark'").ToList(); FiddleHelper.WriteTable(customer); } //== 多次插入 string sql = "INSERT INTO Customers (CustomerName) Values (@CustomerName);"; using (var connection = new SqlConnection(FiddleHelper.GetConnectionStringSqlServerW3Schools())) { connection.Open(); var affectedRows = connection.Execute(sql, new[] { new {CustomerName = "John"}, new {CustomerName = "Andy"}, new {CustomerName = "Allan"} } );这是执行插入的示例。
string sql = "UPDATE Categories SET Description = @Description WHERE CategoryID = @CategoryID;"; using (var connection = new SqlConnection(FiddleHelper.GetConnectionStringSqlServerW3Schools())) { var affectedRows = connection.Execute(sql,new {CategoryID = 1, Description = "Soft drinks, coffees, teas, beers, mixed drinks, and ales"}); Console.WriteLine(affectedRows); }更新。
string sql = "DELETE FROM Customers WHERE CustomerID = @CustomerID"; using (var connection = new SqlConnection(FiddleHelper.GetConnectionStringSqlServerW3Schools())) { var affectedRows = connection.Execute(sql, new {CustomerID = 1}); Console.WriteLine(affectedRows); }删除。
Execute没什么好说的，基本就是执行SQL语句的形式完成增删改成等操作。
值得注意的是：
public static IDataReader ExecuteReader(this IDbConnection cnn, string sql, object param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null);返回一个IDataReader实例，这个实例可以给DataTable填充数据，使用方法如下：
DataTable table = new DataTable(); table.Load(reader);以及：
public static T ExecuteScalar<T>(this IDbConnection cnn, string sql, object param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null);这个方法是返回查询结果的第一行第一列的元素。
6. 总结如果单说Dapper的话，并没有太多好说的。不过Dapper是真的快，在实际开发中有时候会用Dapper作为EF Core的一个补充。
当然了，Dapper还有很多其他的插件，使用那些插件可以为Dappe带来非一般的提升。我们下一篇将介绍一下Dapper的插件。
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