Question

我有一个表单，系统管理员使用保存按钮将数据输入到tblministries表（例如A B C D E F）。当表单加载时，A B C D E F加载到checkedlistbox（cblMinistries）。用户可以检查checkedlistbox中的任何数据（例如B C F），然后使用用户成员ID将其保存到tblMembershipministry表中。当成员输入其ID并单击搜索按钮时，表单应将A B C D E F加载到checkedlistbox中，并且应在checklistbox中检查来自tblMembershipministry表（B C F）的具有相同成员ID的任何数据。我的问题是我不断收到错误“无法将对象强制转换为'System.String'以在此代码行上键入'System.Data.DataRowView'”DataRowView row =（DataRowView）this.cblMinistries.Items [i] ;“请帮帮我

用于填充核对表列表的代码

public void PopuMinistry()
    {
        SqlConnection conn = new SqlConnection("Data Source=USER-PC;Initial Catalog=PIWCDB;User ID=sa;Password=mike");
        if (conn.State != ConnectionState.Open)
        {
            conn.Open();
        }
        string SqlDataPull = ("select Homecellname from tblministries order by Homecellname");

        SqlCommand cmd = new SqlCommand(SqlDataPull);
        cmd.Connection = conn;
        cmd.CommandType = CommandType.Text;
        SqlDataReader dr = cmd.ExecuteReader();


        while (dr.Read())
        {
            SqlDataPull = dr[0].ToString();
            cblMinistries.Items.Add(SqlDataPull);
        }
        dr.Close();
    }

将checklistbox项目标记为已检查的代码

public void minsearch()
    {
        SqlConnection conn = new SqlConnection(ConfigurationSettings.AppSettings["ConnectionString"]);
        conn.ConnectionString = "Data Source=USER-PC;Initial Catalog=PIWCDB;User ID=sa;Password=mike";
        conn.Open();

        string sqlQuery = "SELECT Ministryname FROM tblMembershipministry WHERE FormattedMembershipid = '" + this.txtMembershipid.Text + "'";
        SqlCommand cmd = new SqlCommand();
        cmd.Connection = conn;
        cmd.CommandText = sqlQuery;
        cmd.CommandType = System.Data.CommandType.Text;

        try
        {
            System.Data.SqlClient.SqlDataReader dr = null;
            dr = cmd.ExecuteReader();

            while (dr.Read())
            {
                for (int i = 0; i < cblMinistries.Items.Count; i++)
                {
                    DataRowView row = (DataRowView)this.cblMinistries.Items[i];

                    if (row[cblMinistries.ValueMember].ToString() == dr["Ministryname"].ToString())
                    {
                        cblMinistries.SetItemChecked(i, true);
                    }                     
                }
            }

            dr.Close();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }

Answer 1

string SqlDataPull = ("select Homecellname from tblministries order by Homecellname");
...
cblMinistries.Items.Add(SqlDataPull);

因此，

DataRowView row = (DataRowView)this.cblMinistries.Items[i]

正在尝试将字符串转换为DataRowView。

也许以下内容可行：

string ministryValue = this.cblMinistries.Items[i] ;
if (ministryValue  == dr["Ministryname"].ToString())
                    {
                        cblMinistries.SetItemChecked(i, true);
                    }

Answer 2

已检查的列表框未填充数据行，但读取器返回的第一列的字符串（Homecellname）。

这意味着，您可以直接将项目转换为字符串，前提是您需要该值（在代码中使用cblMinistries.ValueMember，我假设它引用了Homecellname）

 string tofind = dr["Ministryname"].ToString();
 for (int i = 0; i < cblMinistries.Items.Count; i++)
 {
      string ministry = (string)this.cblMinistries.Items[i];

      if (ministry  == tofind)
      {
           cblMinistries.SetItemChecked(i, true);
      }                     
  }

解析错误消息无法将对象强制转换为类型'System.String'以键入'System.Data.DataRowView'

2 个答案: