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[英]Unable to cast object of type 'System.Data.DataRowView' to type 'System.String'
[英]resolving error message Unable to cast object to type 'System.String' to type 'System.Data.DataRowView'
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ABCDEF)中。 加载表单时,ABCDEF加载到清单列表框(cblMinistries)。 用户可以检查清单列表中的任何数据(例如BCF),然后将其与用户成员ID一起保存到tblMembershipministry表中。 当成员输入其ID并单击搜索按钮时,该表单应将ABCDEF加载到清单列表框中,并且应在清单框中检查tblMembershipministry表(BCF)中具有相同成员ID的任何数据。 我的问题是我在此代码行“ DataRowView row =(DataRowView)this.cblMinistries.Items [i]”上始终收到错误消息“无法将对象键入'System.String'键入'System.Data.DataRowView'”。 ;”请帮帮我
用于填充清单框的代码
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();
}
将清单框项目标记为已选中的代码
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);
}
}
string SqlDataPull = ("select Homecellname from tblministries order by Homecellname");
...
cblMinistries.Items.Add(SqlDataPull);
从而,
DataRowView row = (DataRowView)this.cblMinistries.Items[i]
正在尝试将字符串转换为DataRowView
。
也许以下方法会起作用:
string ministryValue = this.cblMinistries.Items[i] ;
if (ministryValue == dr["Ministryname"].ToString())
{
cblMinistries.SetItemChecked(i, true);
}
选中的列表框未填充数据行,而是填充了读取器返回的第一列的字符串( Homecellname
)。
这意味着,您可以将项目直接转换为字符串,并提供所需的值(您在代码中使用cblMinistries.ValueMember,我假设它引用的是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);
}
}
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