C＃返回值

Question

我的連接字符串：

string connection = @"Provider=Microsoft.ACE.OLEDB.12.0;" + 
    @"Data Source=\\reso-fs-2\allusers\Student_Home\20350657\Documents\clicker.accdb;" + 
    @"Jet OLEDB:Database Password=" + "password" + ";"; 

OleDbConnection con = new OleDbConnection(connection); 

所以我有這個疑問在C＃中OLEDB：

string query = "SELECT stats_best FROM Users WHERE username="+GameForm.username; 

我想獲取從 'stats_best' 的價值和將其保存到一個字符串中。 我已經建立了連接和所有。我只需要從查詢中返回一個值。 我該怎麼做？

Answer 1

請閱讀this文章，但無論如何，你可以使用這個

public string Test(string userName, string connectionString, out string dbErrorMessage) 
    { 
     string result = null; 
     dbErrorMessage = null; 
     try 
     { 
      using (SqlConnection connection = new SqlConnection(connectionString)) 
      { 
       connection.Open(); 
       SqlCommand cmd = connection.CreateCommand(); 
       cmd.Parameters.Add(new SqlParameter("@UserName", userName)); 
       cmd.CommandText = "SELECT stats_best FROM Users WHERE username= @UserName"; 
       result = cmd.ExecuteScalar().ToString(); 
      } 
     } 
     catch (Exception ex) 
     { 
      dbErrorMessage = ex.Message; 
     } 
     return result; 
    } 

和方法的用法：

string dbErrorMessage = null; 
Test(GameForm.username, connectionString, out dbErrorMessage); 

Answer 2

private string Func(GameForm GameForm){ 

       DataTable table ; 
       string connectionString = //"connection string"; 
       string query = "SELECT stats_best FROM Users WHERE username=" + GameForm.username; 

       SqlConnection sqlConnection = new SqlConnection(connectionString);   
       SqlCommand sCmd = new SqlCommand(query, sqlConnection); 
       sqlConnection.Open(); 

       SqlDataAdapter dataAdapt= new SqlDataAdapter(sCmd); 

       dataAdapt.Fill(table); 
       sqlConnection.Close(); 
       dataAdapt.Dispose(); 
       return table.ToString(); 
      }