Question

C#winform中如何判断用户ID是否存在？存在时清理原有的值，下面是相关代码

public static class LoginInfo
{
/// <summary>
/// 用户登录信息
/// </summary>
public static Web_User Value()
{
string _connStr = string.Empty;
string uid = string.Empty;
bool flag = false;
Web_User user = null;
DataSet ds = null;
DataRow dr = null;
SqlDataAdapter daSql = null;
SqlCommand dbCmd = null;
SqlConnection dbConn = null;
try
{
user = new Web_User();
//判断原用户ID是否存在
flag = (["MemberPage_UID"] != null);
if(flag)
{
flag = (["MemberPage_UID"].Value != "");
}
if(flag)
{
//存在时清理原有的值
uid = (["MemberPage_UID"].Value);
//获取用户信息
ds = new DataSet();
daSql = new SqlDataAdapter();
dbCmd = new SqlCommand();
_connStr = ConfigInfo.Connstring;
dbConn = new SqlConnection(_connStr);
dbConn.Open();
dbCmd.CommandText = "SELECT * FROM Web_User WHERE [Name] = '" + uid + "'";
dbCmd.CommandType = CommandType.Text;
dbCmd.Connection = dbConn;
dbCmd.ExecuteNonQuery();
daSql.SelectCommand = dbCmd;
daSql.Fill(ds);
dr = ds.Tables[0].Rows[0];

Answer 1

如果只是删除数据库中的值：
dbCmd.CommandText = "delete FROM Web_User WHERE [Name] = '" + uid + "'"；
如果是判断该用户ID在数据库存在，存在就删除其查询结果的值
DataTable tb = new DataTable();
DataRow[] l_drArray = tb.Select("name = '" + uid + "'");
if (l_drArray.Length > 0)
{
tb.Rows.Remove(l_drArray[0]);
}

追问

我是要判断做登陆使用啊不是删除

追答

你的意思是存在时更新其原来的值？

追问

存在时清除上次登陆的值啊

追答

你上次登录的值保存在哪儿了？数据库还是