SqlConnection sqlCon = new SqlConnection(@"Server =(local);Integrated Security = True;"+"Database = IT登陆");
sqlCon.Open();
SqlCommand sqlCom = new SqlCommand();
sqlCom.Connection = sqlCon;
sqlCom.CommandText ="SELECT * FROM 用户信息 WHERE IT号码 = '"+this.comboBox1.Text +"'AND IT密码 ='"+textBox2.Text+"'";
SqlDataReader thisReader = sqlCom.ExecuteReader();

在外面加个 try..catch...试试.

  里面的格式有错误

new SqlConnection(@"Server =(local);Integrated Security = True;"+"Database = IT登陆");
这个不完整吧?UserID,Pwd加上看

楼上滴，不用uid和pwd也可以的。用滴是windows集成验证。
楼主可以综合一下2楼和3楼的把sql语句输出试下
try
{
SqlDataReader thisReader = sqlCom.ExecuteReader();
}
catch
{
输出你的sql语句。然后在查询分析器中试下。
}

SqlCommand sqlCom = new SqlCommand();
sqlCom.Connection = sqlCon;


=========================================
SqlCommand sqlCom=SqlCon.CreateCommand();

"SELECT * FROM 用户信息 WHERE IT号码 = "+"'"+this.comboBox1.Text +"'"+"AND IT密码 ="+"'"+textBox2.Text+"'";