你是想学sql语句?还是在C#中对数据库的操作阿?
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如果是想通过.net进行数据库的访问,msdn上面说的很清楚
using System.Data;
using System.Data.SqlClient;.......................public void ReadMyData(string myConnString) {
string mySelectQuery = "SELECT OrderID, CustomerID FROM Orders";
SqlConnection myConnection = new SqlConnection(myConnString);
SqlCommand myCommand = new SqlCommand(mySelectQuery,myConnection);
myConnection.Open();
SqlDataReader myReader;
myReader = myCommand.ExecuteReader();
// Always call Read before accessing data.
while (myReader.Read()) {
Console.WriteLine(myReader.GetInt32(0) + ", " + myReader.GetString(1));
}
// always call Close when done reading.
myReader.Close();
// Close the connection when done with it.
myConnection.Close();
}
{
SqlConnection myConnection;
myConnection = new SqlConnection( ConnectString);
SqlDataAdapter myCommand = new SqlDataAdapter(sql_str, myConnection);
DataSet ds = new DataSet();
myCommand.Fill(ds, "t1");
return ds.Tables ["t1"]; }
在程序中调用:
string sql="select * from tablename ";
DataTable dt=Public_Class.Get_Select_Table(sql)
public void ReadMyData(string myConnString)
{
string mySelectQuery = "SELECT OrderID, Customer FROM Orders";
SqlConnection myConnection = new SqlConnection(myConnString);
SqlCommand myCommand = new SqlCommand(mySelectQuery,myConnection);
myConnection.Open();
SqlDataReader myReader = myCommand.ExecuteReader();
try
{
while (myReader.Read())
{
Console.WriteLine(myReader.GetInt32(0) + ", " + myReader.GetString(1));
}
}
finally
{
// always call Close when done reading.
myReader.Close();
// always call Close when done reading.
myConnection.Close();
}
}
TextBox2.Text = myreader.GetString(1);
TextBox3.Text = Convert.ToString(myreader.GetInt32(2));里面有这样的语句,但执行它的时候出现:
在没有任何数据时进行无效的读取尝试。
说明: 执行当前 Web 请求期间,出现未处理的异常。请检查堆栈跟踪信息,以了解有关该错误以及代码中导致错误的出处的详细信息。 异常详细信息: System.InvalidOperationException: 在没有任何数据时进行无效的读取尝试。源错误:
行 182: con.Open();
行 183: SqlDataReader myreader = selcommand.ExecuteReader();
这里开始出错:行 184: TextBox1.Text = Convert.ToString(myreader.GetInt32(0));
行 185: TextBox2.Text = myreader.GetString(1);
行 186: TextBox3.Text = Convert.ToString(myreader.GetInt32(2));
怎么解决??
SqlConnection con = new SqlConnection("data source = localhost; database = mydb; uid = sa; pwd =");
SqlCommand selcommand = new SqlCommand(cmdstring,con);
con.Open();
SqlDataReader myreader = selcommand.ExecuteReader();
string id1 = Convert.ToString(myreader.GetString(0));
TextBox1.Text = id1;
string address1 = myreader.GetString(1);
TextBox2.Text = address1;
string tel1 = Convert.ToString(myreader.GetString(2));
TextBox3.Text = tel1;
myreader.Close();
con.Close();
到底是什么问题呀??:<有人愿意指点 一下吗?