ASP.NET Core3.0(一) --使用普通方法连接数据库
一、新建一个.NET Core的工程 文件
二、新建sqlHelper类
需要使用NuGet安装一下文件
- System.Data.SqlClient
- Microsoft.EntityFrameworkCore
以下代码较长，可以先粘贴复制，以后再仔细打磨
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Options;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.IO;
using System.Linq;
using System.Web;
namespace CORE3.Common
{
/// 此类为抽象类，
/// 不允许实例化，在应用时直接调用即可
///
public abstract class SqlHelper
{
//加载appsetting.json
static IConfiguration configuration = new ConfigurationBuilder()
.SetBasePath(Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json").Build();
/// 返回一个数值表示此SqlCommand命令执行后影响的行数
public static int ExecteNonQuery(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
{
SqlCommand cmd = new SqlCommand();
using (SqlConnection conn = new SqlConnection(connectionString))
{
//通过PrePareCommand方法将参数逐个加入到SqlCommand的参数集合中
PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
int val = cmd.ExecuteNonQuery();
//清空SqlCommand中的参数列表
cmd.Parameters.Clear();
return val;
}
}
/// 返回一个数值表示此SqlCommand命令执行后影响的行数
public static int ExecteNonQuery(CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
{
return ExecteNonQuery(connectionString, cmdType, cmdText, commandParameters);
}
/// 返回一个数值表示此SqlCommand命令执行后影响的行数
public static int ExecteNonQueryProducts(string cmdText, params SqlParameter[] commandParameters)
{
return ExecteNonQuery(CommandType.StoredProcedure, cmdText, commandParameters);
}
/// 返回一个数值表示此SqlCommand命令执行后影响的行数
public static int ExecteNonQueryText(string cmdText, params SqlParameter[] commandParameters)
{
return ExecteNonQuery(CommandType.Text, cmdText, commandParameters);
}
#endregion
#region//GetTable方法
/// 返回一个表集合(DataTableCollection)表示查询得到的数据集
public static DataTableCollection GetTable(string connecttionString, CommandType cmdTye, string cmdText, SqlParameter[] commandParameters)
{
SqlCommand cmd = new SqlCommand();
DataSet ds = new DataSet();
using (SqlConnection conn = new SqlConnection(connecttionString))
{
PrepareCommand(cmd, conn, null, cmdTye, cmdText, commandParameters);
SqlDataAdapter adapter = new SqlDataAdapter();
adapter.SelectCommand = cmd;
adapter.Fill(ds);
}
DataTableCollection table = ds.Tables;
return table;
}
/// 返回一个表集合(DataTableCollection)表示查询得到的数据集
public static DataTableCollection GetTable(CommandType cmdTye, string cmdText, SqlParameter[] commandParameters)
{
return GetTable(connectionString, cmdTye, cmdText, commandParameters);
}
/// 返回一个表集合(DataTableCollection)表示查询得到的数据集
public static DataTableCollection GetTableProducts(string cmdText, SqlParameter[] commandParameters)
{
return GetTable(CommandType.StoredProcedure, cmdText, commandParameters);
}
/// 返回一个表集合(DataTableCollection)表示查询得到的数据集
public static DataTableCollection GetTableText(string cmdText, SqlParameter[] commandParameters)
{
return GetTable(CommandType.Text, cmdText, commandParameters);
}
#endregion
/// A SqlDataReader containing the results
public static SqlDataReader ExecuteReader(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
{
SqlCommand cmd = new SqlCommand();
SqlConnection conn = new SqlConnection(connectionString);
// we use a try/catch here because if the method throws an exception we want to
// close the connection throw code, because no datareader will exist, hence the
// commandBehaviour.CloseConnection will not work
try
{
PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
SqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
cmd.Parameters.Clear();
return rdr;
}
catch
{
conn.Close();
throw;
}
}
#region//ExecuteDataSet方法
/// return a dataset
public static DataSet ExecuteDataSet(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
{
SqlConnection conn = new SqlConnection(connectionString);
SqlCommand cmd = new SqlCommand();
try
{
PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
SqlDataAdapter da = new SqlDataAdapter();
DataSet ds = new DataSet();
da.SelectCommand = cmd;
da.Fill(ds);
return ds;
}
catch
{
conn.Close();
throw;
}
}
/// return a dataset
public static DataSet ExecuteDataSet(CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
{
return ExecuteDataSet(connectionString, cmdType, cmdText, commandParameters);
}
/// return a dataset
public static DataSet ExecuteDataSetProducts(string cmdText, params SqlParameter[] commandParameters)
{
return ExecuteDataSet(connectionString, CommandType.StoredProcedure, cmdText, commandParameters);
}
/// return a dataset
public static DataSet ExecuteDataSetText(string cmdText, params SqlParameter[] commandParameters)
{
return ExecuteDataSet(connectionString, CommandType.Text, cmdText, commandParameters);
}
public static DataView ExecuteDataSet(string connectionString, string sortExpression, string direction, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
{
SqlConnection conn = new SqlConnection(connectionString);
SqlCommand cmd = new SqlCommand();
try
{
PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
SqlDataAdapter da = new SqlDataAdapter();
DataSet ds = new DataSet();
da.SelectCommand = cmd;
da.Fill(ds);
DataView dv = ds.Tables[0].DefaultView;
dv.Sort = sortExpression + " " + direction;
return dv;
}
catch
{
conn.Close();
throw;
}
}
#endregion
#region // ExecuteScalar方法
/// 返回一个对象
public static object ExecuteScalar(CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
{
return ExecuteScalar(SqlHelper.connectionString, cmdType, cmdText, commandParameters);
}
/// 返回一个对象
public static object ExecuteScalarProducts(string cmdText, params SqlParameter[] commandParameters)
{
return ExecuteScalar(SqlHelper.connectionString, CommandType.StoredProcedure, cmdText, commandParameters);
}
/// 返回一个对象
public static object ExecuteScalarText(string cmdText, params SqlParameter[] commandParameters)
{
return ExecuteScalar(SqlHelper.connectionString, CommandType.Text, cmdText, commandParameters);
}
/// An object that should be converted to the expected type using Convert.To{Type}
public static object ExecuteScalar(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
{
SqlCommand cmd = new SqlCommand();
using (SqlConnection connection = new SqlConnection(connectionString))
{
PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
object val = cmd.ExecuteScalar();
cmd.Parameters.Clear();
return val;
}
}
/// An object that should be converted to the expected type using Convert.To{Type}
public static object ExecuteScalar(SqlConnection connection, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
{
SqlCommand cmd = new SqlCommand();
PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
object val = cmd.ExecuteScalar();
cmd.Parameters.Clear();
return val;
}
#endregion
/// Cached SqlParamters array 缓存参数数组
public static SqlParameter[] GetCachedParameters(string cacheKey)
{
SqlParameter[] cachedParms = (SqlParameter[])parmCache[cacheKey];
if (cachedParms == null)
return null;
SqlParameter[] clonedParms = new SqlParameter[cachedParms.Length];
for (int i = 0, j = cachedParms.Length; i < j; i++)
clonedParms[i] = (SqlParameter)((ICloneable)cachedParms[i]).Clone();
return clonedParms;
}
/// bool结果
public static bool Exists(string strSql)
{
int cmdresult = Convert.ToInt32(ExecuteScalar(connectionString, CommandType.Text, strSql, null));
if (cmdresult == 0)
{
return false;
}
else
{
return true;
}
}
/// bool结果
public static bool Exists(string strSql, params SqlParameter[] cmdParms)
{
int cmdresult = Convert.ToInt32(ExecuteScalar(connectionString, CommandType.Text, strSql, cmdParms));
if (cmdresult == 0)
{
return false;
}
else
{
return true;
}
}
}
}
三、修改配置文件appsettings.json
{
"Logging": {
"IncludeScopes": false,
"LogLevel": {
"Default": "Warning"
}
},
"DBSetting": {
"ConnectString": "server=.;database=Test;uid=sa;pwd=root"
},
"AllowedHosts": "*"
}
四、编写业务逻辑代码
using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Threading.Tasks;
using CORE3.Common;
using System.Data.SqlClient;
namespace CORE3.DLL
{
public class studentDLL
{
public DataTable GetData()
{
var sql = "select * from Student";
var data = SqlHelper.GetTable(CommandType.Text, sql, new SqlParameter[] {
});
return data[0];
}
}
}
五、前台展示
打开项目自动生成的Pages文件夹里的idex.cshtml文件
(1)在Index.cshtml.cs文件中，编写代码：
using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Threading.Tasks;
using CORE3.DLL;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.Extensions.Logging;
namespace CORE3.Pages
{
public class IndexModel : PageModel
{
private readonly ILogger<IndexModel> _logger;
public IndexModel(ILogger<IndexModel> logger)
{
_logger = logger;
}
public DataTable Data;
public void OnGet()
{
var studentDll = new studentDLL();
Data = studentDll.GetData();
}
}
}
（2）在Index.cshtml文件中编写代码
@page
@model IndexModel
@{
ViewData["Title"] = "Home page";
}
@{
var data = Model.Data;
if (data.Rows.Count > 0)
{
for (int i = 0; i < data.Rows.Count; i++)
{
var row = data.Rows[i];
@row["ID"];
@row["Name"].ToString();
@row["Sex"];
}
}
}
六、数据库文件
七、运行结果
