C# 如何把數據庫內的數據讀取出來並賦值給壹自定義的變量

SqlConnection cnn = new SqlConnection("數據庫連接字符串");

//構造查詢字符串

string str = @"Select top * from A";

//新建SqlCommand對象

SqlCommand cmd = new SqlCommand(str, cnn);

//打開數據庫連接

cnn.Open();

//返回dr對象

SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);

string x = dr["a"].ToString();

string y = dr["b"].ToString();

string z = dr["c"].ToString();