c# - CommandText 属性未初始化

Question

只有在我将工作代码更改为使用数据 View 而不是文本框来显示单行数据之后，我才遇到这个问题。

我有以下内容:

static SqlConnection dbConnection = new SqlConnection
                       (DBConnection.DBConnection.connectionString);        
    SqlDataAdapter holdone = new SqlDataAdapter(getCommand, dbConnection);      

    DataSet holdall = new DataSet();
    DataSet updateall = new DataSet();
    DataTable invoiceTable = new DataTable();

    DataView invoiceView = new DataView();

被使用

public void GetOne(/* connectionString, string invref, string tableref*/)
    {

getCommand = "select *redacted* from " + tableref +  
                                      "where *redacted* = " + invref;

        using (SqlConnection dbConnection = new SqlConnection
                               (DBConnection.DBConnection.connectionString))
        {
                dbConnection.Open();

            holdone.Fill(holdall);

            invoiceTable = holdall.Tables[0];

            dbConnection.Close();


        }

        DataRowView rowView = invoiceView.AddNew();

            rowView["*redacted*"] = invoiceTable;

            rowView.EndEdit();
    }

错误报告 holdone.fill(holdall) 作为违规行，但是我不确定为什么，因为我没有使用 SQLCommand 作为参数，而不是 SQLDataAdapter 的参数。

我正在努力寻找哪里出了问题？

Answer 1

问题是您确实将SqlDataAdapter 的选择命令字符串设置为getCommand 的当前 值> 在这一行中:

SqlDataAdapter holdone = new SqlDataAdapter(getCommand, dbConnection); 

但是，由于字符串并不是真正的指针，因此更改 getCommand 后记将不会更改 SqlDataAdapter 的选择命令。

您需要做的是:

public void GetOne(/* connectionString, string invref, string tableref*/)
{

    getCommand = "select *redacted* from " + tableref + "where *redacted* = " + invref;
    using (SqlConnection dbConnection = new SqlConnection(DBConnection.DBConnection.connectionString))
    {
        dbConnection.Open();

        holdone.SelectCommand = new SqlCommand(getCommand, dbConnection);
        holdone.Fill(holdall);

        invoiceTable = holdall.Tables[0];
        //dbConnection.Close(); // This line is unnecessary, as the connection will be closed by `using`
    }

    DataRowView rowView = invoiceView.AddNew();
    rowView["*redacted*"] = invoiceTable;
    rowView.EndEdit();
}