public DataRow dr; public void datBD()
{
MySqlConnection mysqlcon = new MySqlConnection("Server=localhost;userid=root;password=1234;Database=zhwedo");
mysqlcon.Open();
//MySqlCommand mysqlcmd = new MySqlCommand("select uname from sdb_members where uname='" + usname + "' ", mysqlcon);
string mysqlcmd="select * from sdb_members where uname='" + usname + "'";
MySqlDataAdapter date = new MySqlDataAdapter(mysqlcmd, mysqlcon);
DataSet ds = new DataSet();
date.Fill(ds, "mymuma");
dr = ds.Tables["mymama"].Rows[0];//这里出现未处理NullReferenceException :未将对象引用设置到对象的实例 ...
this.Luname.Text = dr["usname"].ToString();
this.lemail.Text = dr["email"].ToString();
this.Textname.Text = dr["name"].ToString();
}
我是一个初学者,这原来这个写法是用在access上的,现在我用在mysql上了!
{
MySqlConnection mysqlcon = new MySqlConnection("Server=localhost;userid=root;password=1234;Database=zhwedo");
mysqlcon.Open();
//MySqlCommand mysqlcmd = new MySqlCommand("select uname from sdb_members where uname='" + usname + "' ", mysqlcon);
string mysqlcmd="select * from sdb_members where uname='" + usname + "'";
MySqlDataAdapter date = new MySqlDataAdapter(mysqlcmd, mysqlcon);
DataSet ds = new DataSet();
date.Fill(ds, "mymuma");
dr = ds.Tables["mymama"].Rows[0];//这里出现未处理NullReferenceException :未将对象引用设置到对象的实例 ...
this.Luname.Text = dr["usname"].ToString();
this.lemail.Text = dr["email"].ToString();
this.Textname.Text = dr["name"].ToString();
}
我是一个初学者,这原来这个写法是用在access上的,现在我用在mysql上了!
{
dr = ds.Tables["mymama"].Rows[0];
...
}
所以先做一下判断
if(ds.Tables["mymama"].Rows.Count>0)
{
dr = ds.Tables["mymama"].Rows[0];
}
{ }
判断表是否为空,为空则不进行赋值操作
DataSet ds = new DataSet();
date.Fill(ds, "mymuma");
DataRow[] row = ds.Tables[0].Select();
foreach (DataRow dr in row)
{
this.Luname.Text = dr["usname"].ToString();
this.lemail.Text = dr["email"].ToString();
this.Textname.Text = dr["name"].ToString();
}
DataRow[] row = ds.Tables["mymama"].Select();
dr = ds.Tables["mymama"].NewRow();
dr = ds.Tables["mymama"].Rows[0];//这里出现未处理NullReferenceException :未将对象引用设置到对象的实例 ...
dr = ds.Tables["mymama"].NewRow(); 列“usname”不属于表 mymama。
出现这个错误,但是是有这个字段的