SqlDataReader dr = cmd.ExecuteReader();
while(dr.Read())
{
if(!dr.IsDBNull(3)){//先判断是否为空
txtCompany.Text = dr.GetString(3); //当值为null时出错
}
}
while(dr.Read())
{
if(!dr.IsDBNull(3)){//先判断是否为空
txtCompany.Text = dr.GetString(3); //当值为null时出错
}
}
.....