急c#怎么把数据库查询语句的值读出来赋给变量

急急急！！在线等，c#如何把数据库查询语句的值读出来赋给变量
数据库查询语句为：
string strsql6 = "select count(sno) from student where cno='" + class1 + "' and cet4>425";
想把查询后的值赋给TextBox;

[解决办法]

C# code

Sqlcommond cmd =new Sqlcommond();textBox.Text=cmd.ExecuteScalar().ToString();
[解决办法]
C# code
using System.Data.SqlClient;using(SqlConnection con = new SqlConnection("Data Source=.;uid=sa;pwd=sa;Database=Northwind")){    con.Open();    string strsql6 = "select count(sno) from student where cno='" + class1 + "' and cet4>425";    SqlCommand cmd = new SqlCommand(strsql6,con);     this.TextBox1.Text = cmd.ExecuteScalar().ToString();}
[解决办法]
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C# code


using System.Data.SqlClient;

using(SqlConnection con = new SqlConnection("Data Source=.;uid=sa;pwd=sa;Database=Northwind"))
{
    con.Open();
    string strsql6 = "select count(sno)……

[解决办法]
楼上的只针对了楼主的例子情况，多字段的话，要参考ExecuteReader或者用SqlAdapter的fill方法，装到DataTable里面，然后写for循环，table.Rows[i]["字段名"].ToString()可以读取字段的值
[解决办法]
探讨


C# code

using System.Data.SqlClient;

using(SqlConnection con = new SqlConnection("Data Source=.;uid=sa;pwd=sa;Database=Northwind"))
{
    con.Open();
    string strsql6 = "select count(sno) from s……

[解决办法]
C# code
using System.Data.SqlClient;using(SqlConnection con = new SqlConnection("Data Source=.;initial catalog=Northwind;user id=sa;password=sa")){    string strsql6 = "select count(sno) from student where cno=@class1 and cet4>425";    using(SqlCommand cmd = new SqlCommand(strsql6,con))  {      con.Open();     cmd.Parameters.AddWithValue("@class1",class1);          this.TextBox1.Text = cmd.ExecuteScalar().ToString();  }}