c#关于数据库连接操作的案例
程序中添加了一个XML文件：App.config
<?xml version="1.0"?>
<configuration>
<configSections>
<sectionGroup name="userSettings" type="System.Configuration.UserSettingsGroup, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
<section name="Message.sysFrm" type="System.Configuration.ClientSettingsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" allowExeDefinition="MachineToLocalUser" requirePermission="false"/>
<section name="Message.system" type="System.Configuration.ClientSettingsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" allowExeDefinition="MachineToLocalUser" requirePermission="false"/>
</sectionGroup>
</configSections>
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5"/>
</startup>
<connectionStrings>
<add name="connString" connectionString=";Initial Catalog=Message;User ID=sa;PWD=112442;Connect Timeout=5; "/>
</connectionStrings>
<userSettings>
<Message.sysFrm>
<setting name="sysFirstStart" serializeAs="String">
<value>True</value>
</setting>
<setting name="comSetting" serializeAs="String">
<value />
</setting>
<setting name="portSetting" serializeAs="String">
<value />
</setting>
<setting name="serverSetting" serializeAs="String">
<value />
</setting>
</Message.sysFrm>
<Message.system>
<setting name="comSetting" serializeAs="String">
<value/>
</setting>
</Message.system>
</userSettings>
</configuration>
namespace Message
{
class DBHelper
{
private static sysFrm sysSetting = new sysFrm();//定义应用程序设置文件
public static readonly string connStr = "Data Source=" + sysSetting.serverSetting + System.Configuration.ConfigurationManager.ConnectionStrings["connString"].ConnectionString;
//
public static int ExecuteNonQuery(string sqlStr, params SqlParameter[] param)//ExecuteNonQuery返回受语句影响的行数，如果是select语句则返回-1；
{
int res = 0;
using (SqlConnection conn = new SqlConnection())
{
conn.ConnectionString = connStr;
using (SqlCommand cmd = new SqlCommand())
{
cmd.CommandText = sqlStr;
cmd.Connection = conn;
if (param != null)
cmd.Parameters.AddRange(param);//另一个 SqlParameterCollection 中已包含 SqlParameter。
// 摘要：向 System.Data.SqlClient.SqlParameterCollection 的末尾添加values的数组。
// 参数:values:要添加的 System.Data.SqlClient.SqlParameter 值。
try
{
conn.Open();
res = cmd.ExecuteNonQuery();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
//cmd.Parameters.Clear();//另一个 SqlParameterCollection 中已包含 SqlParameter。可以解决报错问题，但是是否影响性能还有待验证
return res;
}
}
}
public static object ExecuteScalar(string sqlStr, params SqlParameter[] param)//执行查询，并返回查询结果的第一行和第一列
{
using (SqlConnection conn = new SqlConnection())
{
conn.ConnectionString = connStr;
using (SqlCommand cmd = new SqlCommand())
{
cmd.Connection = conn;
cmd.CommandText = sqlStr;
if (param != null)
cmd.Parameters.AddRange(param);
conn.Open();//打开数据库
return cmd.ExecuteScalar();
}
}
}
public static SqlDataReader ExecuteReader(string sqlStr, params SqlParameter[] param)
{
SqlConnection conn = new SqlConnection();
conn.ConnectionString = connStr;
using (SqlCommand cmd = new SqlCommand())
{
cmd.Connection = conn;
cmd.CommandText = sqlStr;
if (param != null)
cmd.Parameters.AddRange(param);
try
{
conn.Open();
}
catch (System.Exception ex)
{
MessageBox.Show("获取网络内数据库服务器和实例出错！" + ex.ToString(), "提示",MessageBoxButtons.OK, MessageBoxIcon.Information);
return null;
}
SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
return dr;
}
}
public static DataTable DataAdapter(string sqlstr, params SqlParameter[] param)
{
SqlDataAdapter da = new SqlDataAdapter(sqlstr, connStr);
DataTable dt = new DataTable();
da.SelectCommand.Parameters.AddRange(param);
//DataSet ds = new DataSet();
da.Fill(dt);
int ias = dt.Rows.Count;
for (int i = 0; i < dt.Rows.Count; ++i)
{
DataRow dr = dt.Rows[i];
}
return dt;
}
}
}
1.就是简单的想执行命令操作，如更新插入等等
string sqlstr = "insert into [Bank_Repairs](number,cardId,repairsTime,repairsType) values(@number,@cardId,@repairsTime,@repairsType)";
SqlParameter[] param =
{
new SqlParameter("@number", SqlDbType.VarChar),
new SqlParameter("@cardId",SqlDbType.NVarChar),
new SqlParameter("@repairsTime", SqlDbType.DateTime),
new SqlParameter("@repairsType", "终端自动")
};
param[0].Value = bankId;
param[1].Value = cardId;//非空字段 插入空值会引起错误
param[2].Value = ntime;
DBHelper.ExecuteNonQuery(sqlstr, param);
2.对数据库进行查询操作
string sqlStr = "select *,[Company].name as '公司名称',[Company].workItem as '工作内容',[Company].directorPhone as '主管电话',[Company].directorName as '主管姓名' from [User] join [Company] on [Company].number = [User].company ";
SqlDataReader dr = DBHelper.ExecuteReader(sqlStr, null);
3.查询数据库中是否有记录
string sqlStr = "select count(*) from [Bank_Repairs] where ([Bank_Repairs].repairsTime between @startTime and @endTime) and number = @bankId";
SqlParameter [] param = {
new SqlParameter("@bankId", bankId),
new SqlParameter("@startTime", startTime),
new SqlParameter("@endTime", endTime)
};
DateTime startTime = DateTime.Now.AddDays(-1);//查询2天之内的记录
DateTime endTime = DateTime.Now;
int res = Convert.ToInt32(DBHelper.ExecuteScalar(sqlStr, param));
isExist = res > 0 ? "ok" : "no";