无法访问其他类(C#Windows窗体、SQL Server Management Studio)中的函数

Question

我正在Visual Studio和SQL Server Management Studio中使用C#Windows窗体应用程序学习数据库连接。

我遇到的问题是无法从SQLConn.cs类访问AddParams((和sqlQueryCmd((函数。我尝试过将访问修饰符从private更改为public，但没有成功。有人能带我到这儿来吗？我不知道我做错了什么。

SQLConn.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;
using Microsoft.Data.SqlClient;
namespace dbConnectivityTest1
{
public class SQLConn
{
public static void Main1(string[] args)
{
using (SqlConnection connString = new SqlConnection("Server=ServerName;Database=DatabaseName;User Id=UserID;rnPassword=Password;"))
{
List<SqlParameter> paramList = new List<SqlParameter>();
string AddParams(string tableName, object insVal)
{
SqlParameter sqlparams = new SqlParameter(tableName, insVal);
paramList.Add(sqlparams);
}
SqlCommand sqlCmd = new SqlCommand();
string sqlQueryCmd(string sqlQuery)
{
int recordCount = 0;
string excptnShow = "";
try
{
connString.Open();
SqlCommand sqlCmd = new SqlCommand(sqlQuery, connString);
paramList.ForEach(p => { sqlCmd.Parameters.Add(p); });
paramList.Clear();
DataTable sqlDT = new DataTable();
SqlDataAdapter sqlDA = new SqlDataAdapter(sqlCmd);
recordCount = sqlDA.Fill(sqlDT);
}
catch(Exception ex)
{
excptnShow = "Error: rn" + ex.Message;
}
finally
{
if (connString.State == ConnectionState.Open)
{
connString.Close();
}
}
}
}
}
}
}

Form1.cs

namespace dbConnectivityTest1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private SQLConn sqlDB = new SQLConn();
private void enterNametextBox_Click(object sender, EventArgs e)
{
enterNametextBox.Clear();
}
private void submitButton_Click(object sender, EventArgs e)
{
while(fullNameTextBox.Text.Length <= 0)
{
MessageBox.Show("Please enter your Full Name!", "Caption", MessageBoxButtons.OKCancel, MessageBoxIcon.Exclamation);
}
while(contactTextBox.Text.Length <= 0)
{
MessageBox.Show("Please enter your Contact Number!", "Caption", MessageBoxButtons.OKCancel, MessageBoxIcon.Exclamation);
}
while(ageTextBox.Text.Length <= 0)
{
MessageBox.Show("Please enter your Age!", "Caption", MessageBoxButtons.OKCancel, MessageBoxIcon.Exclamation);
}
while(emailTextBox.Text.Length <= 0)
{
MessageBox.Show("Please enter your E-mail!", "Caption", MessageBoxButtons.OKCancel, MessageBoxIcon.Exclamation);
}
System.Text.RegularExpressions.Regex emailRegex = new System.Text.RegularExpressions.Regex(@"^[a-zA-Z0-9+_.-]+@[a-zA-Z0-9.-]+$");
while(!emailRegex.IsMatch(emailTextBox.Text))
{
MessageBox.Show("Please enter a valid E-mail!", "Caption", MessageBoxButtons.OKCancel, MessageBoxIcon.Exclamation);
}
InsVal();
}
public void InsVal()
{
**I am trying to call the SQLConn.cs Functions here**
}
}
}

Answer 1

Movint addParam方法/函数无法解决问题，因为SqlParam变量在sqlConn类中不可用。实现目标的更好方法是：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;
using System.Data.SqlClient;
namespace dbConnectivityTest1
{
public class SQLConn
{
private readonly string _connectionString;
private List<SqlParameter> _paramList;
public SQLConn()
{
_connectionString="Server=ServerName;Database=DatabaseName;User Id=UserID;rnPassword=Password;";
_paramList = new List<SqlParameter>();
}
public void AddParams(string tableName, object insVal)
{
SqlParameter sqlparams = new SqlParameter(tableName, insVal);
_paramList.Add(sqlparams);
}
public void sqlQueryCmd(string sqlQuery)
{
using (var sqlConn = new SqlConnection(_connectionString))
{
int recordCount = 0;
string excptnShow = "";
try
{
sqlConn.Open();
SqlCommand sqlCmd = new SqlCommand(sqlQuery, sqlConn);
_paramList.ForEach(p => { sqlCmd.Parameters.Add(p); });
_paramList.Clear();
DataTable sqlDT = new DataTable();
SqlDataAdapter sqlDA = new SqlDataAdapter(sqlCmd);
recordCount = sqlDA.Fill(sqlDT);
}
catch (Exception ex)
{
excptnShow = "Error: rn" + ex.Message;
}
finally
{
if (sqlConn.State == ConnectionState.Open)
{
sqlConn.Close();
}
}
}
}

}

}

在这种情况下，不需要Main方法，因为每个应用程序只能有一个Main方法，而winForms默认情况下已经有一个Main方法。

其次SQLConn类可以具有List类型的私有字段，以及一个名为AddParam的公共方法，其职责是向其添加新的params

最后，添加了一个公共的SqlQueryCmd方法来完成其余的工作。

现在可以使用这个类来执行查询，如下所示：

private void button1_Click(object sender, EventArgs e)
{
var sqlConn = new SQLConn();
sqlConn.AddParams("tableName","your Object");
sqlConn.AddParams("tableName","your Object");
sqlConn.AddParams("tableName","your Object");
sqlConn.sqlQueryCmd("Query");
}