Entity Framework Core执行存储过程_executesqlrawasync

 

目录

1 存储过程

2 存储过程返回多个数据集

3 使用ExecuteSqlRawAsync()执行存储过程和原生SQL

4 使用ExecuteSqlRawAsync()输出存储过程参数

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这节讲解EF Core中使用FromSqlRaw()& ExecuteCommand() 反复执行存储过程 

1 存储过程

下面存储过程返回指定 name和standard 所有学生，name&standard值通过存储过程的输入参数提供

 
CREATE PROCEDURE [dbo].[sp_GetStudents]
    @Name       VARCHAR(50),
    @Standard   INT
AS
BEGIN
    SELECT * FROM Student Where Name=@Name AND Standard=@Standard
END

Entity Framework Core 使用FromSqlRaw() 方法执行存储过，使用FromSqlRaw()方法时必须为存储过程提供两个参数，因此我们必须使用SqlParameter 数组设置参数

SqlParameter类位于Microsoft.Data.SqlClient命名空间内，下面代码执行存储过程​​​​​​​

var param = new SqlParameter[] {
                        new SqlParameter() {
                            ParameterName = "@Name",
                            SqlDbType =  System.Data.SqlDbType.VarChar,
                            Size = 100,
                            Direction = System.Data.ParameterDirection.Input,
                            Value = "Tony"
                        },
                        new SqlParameter() {
                            ParameterName = "@Standard",
                            SqlDbType =  System.Data.SqlDbType.Int,
                            Direction = System.Data.ParameterDirection.Input,
                            Value = 10
                        }};
List<Student> studentList = context.Student.FromSqlRaw("[dbo].[sp_GetStudents] @Name, @Standard", param).ToList();

2 存储过程返回多个数据集

.FromSqlRaw()方法将从存储过程中获取一条记录，如果存储过程返回多个数据集，我们使用 ExecuteReader() 方法

下面存储过程返回两组数据集，一个是Student表，另一个是StudentAddress表​​​​​​​

 
CREATE PROCEDURE [dbo].[sp_MultiRecordSets]
    @IdStu   INT,
    @IdAdd   INT 
AS
BEGIN
    SELECT * FROM Student Where Id=@IdStu 
    SELECT * FROM StudentAddress WHERE Id=@IdAdd
END

下面代码显示了如何使用ExecuteReader() 方法从这两组数据中获取值​​​​​​​

var param = new SqlParameter[] {
                        new SqlParameter() {
                            ParameterName = "@IdStu",
                            SqlDbType =  System.Data.SqlDbType.Int,
                            Direction = System.Data.ParameterDirection.Input,
                            Value = 5
                        },
                        new SqlParameter() {
                            ParameterName = "@IdAdd",
                            SqlDbType =  System.Data.SqlDbType.Int,
                            Direction = System.Data.ParameterDirection.Input,
                            Value = 10
                        }};
var context = new SchoolContext();
using (var cnn = context.Database.GetDbConnection())
{
    var cmm = cnn.CreateCommand();
    cmm.CommandType = System.Data.CommandType.StoredProcedure;
    cmm.CommandText = "[dbo].[sp_MultiRecordSets]";
    cmm.Parameters.AddRange(param);
    cmm.Connection = cnn;
    cnn.Open();
    var reader = cmm.ExecuteReader();
    while (reader.Read())
    {
       // name from student table 
       string studentName= Convert.ToString(reader["Name"]); 
    }
    reader.NextResult(); //move the next record set
    while (reader.Read())
    {
        // city from student address table
        string city = Convert.ToString(reader["City"]); 
    }
}

注意使用NextResult()移动到下一组数据集

EF Core中三个最重要的概念：

1 DbContext类

2 Migrations

3 Fluent APIs

3 使用ExecuteSqlRawAsync()执行存储过程和原生SQL

EF Core使用ExecuteSqlRawAsync() 方法执行存储过程和原生SQL，但是不像FromSqlRaw()方法，它返回受影响的行数，注意也有一个ExecuteSqlRaw() 同步版本类型的方法

var rowsAffected = await context.Database.ExecuteSqlRawAsync("Update Students set Name = 'Donald Trump' where Id = 5");

4 使用ExecuteSqlRawAsync()输出存储过程参数

我们使用存储过程返回生总个数(@TotalStudents)​​​​​​​

 
CREATE PROCEDURE [dbo].[sp_GetStudentsNew]
    @Name               VARCHAR(50),
    @Standard           INT,
    @TotalStudents      INT            OUTPUT
AS
BEGIN
    SELECT * FROM Student Where Name=@Name AND Standard=@Standard
    SET @TotalStudents= (SELECT COUNT(*) FROM Student)
END

为了执行存储过程在EF Core，我们需要指定SqlParameter参数的输出方向​​​​​​​

new SqlParameter() {
    ParameterName = "@TotalStudents",
    SqlDbType =  System.Data.SqlDbType.Int,
    Direction = System.Data.ParameterDirection.Output, // direction output
}

每次执行存储过程时，我们能通过输出参数获取到返回的值：

int totalStudents = Convert.ToInt32(Convert.ToString(param[2].Value));

注意：参数的开始索引是0，总共有三个参数，最后一个参数是输出参数​​​​​​​

var context = new SchoolContext();
var param = new SqlParameter[] {
                        new SqlParameter() {
                            ParameterName = "@Name",
                            SqlDbType =  System.Data.SqlDbType.VarChar,
                            Size = 100,
                            Direction = System.Data.ParameterDirection.Input,
                            Value = "Tony"
                        },
                        new SqlParameter() {
                            ParameterName = "@Standard",
                            SqlDbType =  System.Data.SqlDbType.Int,
                            Direction = System.Data.ParameterDirection.Input,
                            Value = 10
                        },
                        new SqlParameter() {
                            ParameterName = "@TotalStudents",
                            SqlDbType =  System.Data.SqlDbType.Int,
                            Direction = System.Data.ParameterDirection.Output,
                        }};
int affectedRows = await context.Database.ExecuteSqlRawAsync("[dbo].[sp_GetStudentsNew] @Name, @Standard, @TotalStudents out", param);
int totalStudents = Convert.ToInt32(param[2].Value); 

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