位置 0 处没有行；

Question

帮助我在尝试获取行中分数的特定数据时一直出现此错误。

我的数据库中有以下数据：

PlayerName    Score
qwe            20
keith          0

我在 winform 中有这段代码：

using (SqlConnection conn = new SqlConnection("Data Source=Rogue;Initial Catalog=SoftProject;Integrated Security=True"))
{
    conn.Open();
  try
  {
    String str1 = "";
    using (SqlCommand cmd = new SqlCommand("Select PlayerName,Score from PlayerData where PlayerName = @player", conn))
    {
        cmd.Parameters.AddWithValue("@player", txtPlayer.Text);
        DataTable dataTable= new DataTable();
        dataTable.Load(cmd.ExecuteReader());

        if(dataTable.Rows.Count>0)
        {
            // concatenate the two string and get the table score row
            str1 = String.Concat(str1, (dataTable.Rows[0]["Score"].ToString()));
        }
        else
        {
            //Report error
        }
    }

    conn.Close();
  }
  catch()
  {
     MessageBox.Show("No data");
  }
}

在此处的这段代码中，这使我的系统出现错误：

str1 = String.Concat(str1, (dataTable.Rows[0]["Score"].ToString()));

得到'qwe'和'20'的名字和分数就可以了；但在第二列 'keith' 和 '0'。我的代码将我标记为错误 "There is no row at position 0";

string.concat 方法 () 似乎有什么问题？

Answer 1

试试这个：

if(dt.Rows.Count>0)
{
str1 = String.Concat(str1, (dataTable.Rows[0]["Score"].ToString()));
}

Answer 2

只使用 SqlDatareader 就足够了

using (SqlConnection conn = new SqlConnection("Data Source=Rogue;Initial Catalog=SoftProject;Integrated Security=True"))
        {           
            conn.Open();
            try
            {
                String str1 = "";
                using (SqlCommand cmd = new SqlCommand("Select PlayerName,Score from PlayerData where PlayerName = @player", conn))
                {
                    cmd.Parameters.AddWithValue("@player", txtPlayer.Text);
                    SqlDataReader reader = cmd.ExecuteReader();

                    if(reader.Read())
                    {
                        str1 = String.Concat(str1, reader.GetString(reader.GetOrdinal("Score")));
                    }
                    else
                    {

                    }
                }
                conn.Close();
            }
            catch
            {

            }

        }

Answer 3

使用此代码

using (SqlConnection conn = new SqlConnection("Data Source=Rogue;Initial Catalog=SoftProject;Integrated Security=True"))
{
conn.Open();
try
{
String str1 = "";
using (SqlCommand cmd = new SqlCommand("Select PlayerName,Score from PlayerData where PlayerName = @player", conn))
{
    cmd.Parameters.AddWithValue("@player", txtPlayer.Text);
    DataSet ds= new DataSet();
    SqlDataAdapter adapter = new SqlDataAdapter(cmd);
    adapter.Fill(ds);

    if(ds.Tables[0].Rows.Count>0)
    {
        // concatenate the two string and get the table score row
        str1 += ds.Tables[0].Rows[0]["Score"].ToString();
    }
    else
    {
        //Report error
    }
    }

    conn.Close();
  }
  catch()
  {
     MessageBox.Show("No data");
  }
}

位置 0 处没有行；

There is no row at position 0;

c#

string-concatenation