// ExecuteNonQuery 构建public static int ExecuteNonQuery(string sql,params SqlParameter[] parameters){    string Str = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;    using (SqlConnection conn = new SqlConnection(Str))    {    conn.Open();    using (SqlCommand cmd = conn.CreateCommand())    {        cmd.CommandText = sql;        foreach (SqlParameter par in parameters)        {        cmd.Parameters.Add(par);        }        return cmd.ExecuteNonQuery();    }    }    }// ExecuteNonQuery 方法的使用private void button1_Click(object sender, EventArgs e)  //单击事件{    try    {    SQLHelper.ExecuteNonQuery("insert into T_Age(Name,Age) values(@N,@A)", new SqlParameter("@N", txtLogin.Text.Trim()), new SqlParameter("@A", txtAge.Text.Trim()));     MessageBox.Show("插入成功！");    }    catch (Exception ex)    {    MessageBox.Show(string.Format("插入失败！:{0}", ex));                return;    }}//-----------------------------------------------------------------------------// ExecuteScalar 构建public static object ExeccuteScalar(string sql, params SqlParameter[] parameters){    string Str = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;    using (SqlConnection conn = new SqlConnection(Str))    {    conn.Open();    SqlCommand cmd = conn.CreateCommand();    cmd.CommandText = sql;    foreach (SqlParameter par in parameters)     {        cmd.Parameters.Add(par);     }     return cmd.ExecuteScalar();    }}// ExecuteScalar 方法的使用private void button2_Click(object sender, EventArgs e)  //单击事件{   int i = Convert.ToInt32(SQLHelper.ExeccuteScalar("select count(*) T_phone"));   MessageBox.Show(Convert.ToString(i));}//-----------------------------------------------------------------------------// ExecuteReader 构造 // 不能使用 usingpublic static SqlDataReader SqlDataReader(string sql, params SqlParameter[] parameters){    string Str = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;    SqlConnection conn = new SqlConnection(Str);    conn.Open();    SqlCommand cmd = conn.CreateCommand();    cmd.CommandText = sql;    foreach (SqlParameter par in parameters)    {      cmd.Parameters.Add(par);    }    SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);    cmd.Parameters.Clear();    return dr;}// ExecuteReader 方法的使用private void button4_Click(object sender, EventArgs e)  //单击事件{  SqlDataReader dr = SQLHelper.SqlDataReader_using("select * from T_Age");  while (dr.Read())  {      MessageBox.Show(Convert.ToString(dr["Name"]));  //读取Name字段的值  }   }//-----------------------------------------------------------------------------// ExecuteDataSet 的构建public static DataTable ExecuteDataSet(string sql, params SqlParameter[] SqlParmeter){      string Str = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;     using (SqlConnection conn = new SqlConnection(Str))     {     conn.Open();     SqlCommand cmd = conn.CreateCommand();     cmd.CommandText = sql;     foreach (SqlParameter par in SqlParmeter)    //遍历增加 SqlParmeter 参数     {             cmd.Parameters.Add(par);     }     DataSet dataset = new DataSet();     SqlDataAdapter adapter = new SqlDataAdapter(cmd);     adapter.Fill(dataset);     return dataset.Tables[0];     }}// ExecuteDataSet 方法的使用private void button5_Click(object sender, EventArgs e){    DataTable dt = SQLHelper.ExecuteDataSet("select * from T_Age");    for (int i = 0; i < dt.Rows.Count; i++)    {    DataRow row = dt.Rows[i];    string name =Convert.ToString(row["Name"]);    MessageBox.Show(name);    }}//-----------------------------------------------------------------------------注意：SqlDataReader如果用 using 的话，将执行不了，因为在读取数据的时候是在using以外,无法读取      如下是错误的代码 public static SqlDataReader ExecuteReader_using(string sql, params SqlParameter[] parameters){    string Str = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;    using (SqlConnection conn = new SqlConnection(Str))    {    conn.Open();    SqlCommand cmd = conn.CreateCommand();    cmd.CommandText = sql;    foreach (SqlParameter par in parameters)    {        cmd.Parameters.Add(par);    }    return cmd.ExecuteReader();    }} //-----------------------------------------------------------------------------