为什么我的简单 C# 网站不能使用 GridView 更新到数据库？

Question

我有以下 C# 来更新记录，但是文本框显示，但不会更新到数据库。同样，我也无法添加记录。

 private DataTable GetData(SqlCommand cmd)
    {
        DataTable dt = new DataTable();
        SqlConnection con = new SqlConnection(strConnString);
        SqlDataAdapter sda = new SqlDataAdapter();
        cmd.CommandType = CommandType.Text;
        cmd.Connection = con;
        con.Open();
        sda.SelectCommand = cmd;
        sda.Fill(dt);
        return dt;
    }

添加：

protected void AddNewMainPost(object sender, EventArgs e)
{
    string postID = ((TextBox)GridView1.FooterRow.FindControl("txtPostID")).Text; 
    string Name = ((TextBox)GridView1.FooterRow.FindControl("txtSelect")).Text;
    SqlConnection con = new SqlConnection(strConnString);
    SqlCommand cmd = new SqlCommand();
    cmd.CommandType = CommandType.Text;
    cmd.CommandText = "insert into homepageSelection(postID, selectionText) " +
    "values(@postID, @selectionText,);" +
     "select postID,selectionText, from homepageSelection";
    cmd.Parameters.Add("@postID", SqlDbType.VarChar).Value = postID;
    cmd.Parameters.Add("@selectionText", SqlDbType.VarChar).Value = Name;
    GridView1.DataSource = GetData(cmd);
    GridView1.DataBind(); 
}

更新

   protected void UpdateMainPost(object sender, GridViewUpdateEventArgs e)
    {
        string postID = ((Label)GridView1.Rows[e.RowIndex].FindControl("lblpostID")).Text;
        string Name = ((TextBox)GridView1.Rows[e.RowIndex].FindControl("txtSelec")).Text;
        SqlConnection con = new SqlConnection(strConnString);
        SqlCommand cmd = new SqlCommand();
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = "update homepageSelection set selectionText=@selectionText, " +
         "where postID=@postID;" +
         "select postID,selectionText from homepageSelection";
        cmd.Parameters.Add("@postID", SqlDbType.VarChar).Value = postID;
        cmd.Parameters.Add("@selectionText", SqlDbType.VarChar).Value = Name;
        GridView1.EditIndex = -1;
        GridView1.DataSource = GetData(cmd);
        GridView1.DataBind(); 
    }

我在数据库中有两个字段：

Table: homepageSelection Fields: postID and selectionText

Answer 1

正如我从上面的代码中看到的，您在两个查询中都有语法错误，但最重要的是您没有将命令与连接相关联。因此，除非您在 GetData 方法中重新创建连接，否则您的命令将无法执行。

所以，修复语法错误

"select postID,selectionText from homepageSelection";
                           ^^^ comma not valid here

cmd.CommandText = @"update homepageSelection set 
                    selectionText=@selectionText" +
                                               ^^^^  again comma not valid here

cmd.CommandText = "insert into homepageSelection(postID, selectionText) " +
                  "values(@postID, @selectionText);" +
                                                 ^^^ no comma here

编辑：似乎您在 GetData 方法中创建了连接，因此在两个调用方法中不需要它。