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I am searching for (PostId,UserId) into PostLikes table using SqlDataAdapter, if the row is found , I am using SqlCommandBuilder.GetDeleteCommand() to generate the delete instruction and deleting the underlying row, if the row is not found, then I use SqlCommandBuilder.GetInsertCommand() to generate the insert command and inserting the row to the table using SqlDataAdapter.Update(). But the row is not getting inserted to the table in database. Here is what I have done so far

SqlConnection con = new SqlConnection(connectionStrings);
SqlDataAdapter sqlDataAdapter=new SqlDataAdapter("select * from PostLikes where PostId like "
                                                 +postlike.PostId+" and UserId like "
                                                 +postlike.UserId,con);
DataSet ds = new DataSet();
sqlDataAdapter.Fill(ds, "Result");
con.Open();
SqlCommandBuilder sqlCommandBuilder = new SqlCommandBuilder(sqlDataAdapter);
if(ds.Tables["Result"].Rows.Count==1)
{
    sqlDataAdapter.DeleteCommand = sqlCommandBuilder.GetDeleteCommand(true);
    msg = "Data is deleted";
}
else
{
    sqlDataAdapter.InsertCommand = sqlCommandBuilder.GetInsertCommand(true);
    msg = "Data is inserted";
}
sqlDataAdapter.Update(ds, "Result");

and the table
PostLikes(LikeId,PostId,UserId)

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1 回答 1

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有几个问题：

  • 您希望重用相同的命令来检测该行是否存在，并提供SqlAdapter给SqlCommandBuilder.
  • 您应该参数化初始选择查询以防止 SqlInjection 攻击（并且有一点性能优势）。CommandBuilder 将自动参数化Insert/Delete命令
  • 使用 . 创建插入 / 删除命令后SqlCommandBuilder，您需要更改基础数据集，以便在Update.
  • 请注意，许多 Sql 对象已经IDisposable并且应该尽快处理 -using范围在这里有帮助。

.

var postId = 1;
var userId = 1;
string msg;
using (var con = new SqlConnection(@"data source=..."))
using (var selectCommand = new SqlCommand(
 "select LikeId, PostId, UserId from PostLikes WHERE PostId=@PostId AND UserId=@UserId", con))
using (var sqlDataAdapter = new SqlDataAdapter(selectCommand))
using (var ds = new DataSet())
{
    con.Open();
    selectCommand.Parameters.AddWithValue("@PostId", postId);
    selectCommand.Parameters.AddWithValue("@UserId", userId);
    sqlDataAdapter.Fill(ds, "Result");
    using (var sqlCommandBuilder = new SqlCommandBuilder(sqlDataAdapter))
    {
        if (ds.Tables["Result"].Rows.Count == 1)
        {
            sqlDataAdapter.DeleteCommand = sqlCommandBuilder.GetDeleteCommand(true);
            ds.Tables["Result"].Rows[0].Delete();
            msg = "Data will be deleted";
        }
        else
        {
            sqlDataAdapter.InsertCommand = sqlCommandBuilder.GetInsertCommand(true);
            // Null because LikeId is Identity and will be auto inserted
            ds.Tables["Result"].Rows.Add(null, postId, userId);
            msg = "Data will be inserted";
        }
        sqlDataAdapter.Update(ds, "Result");
    }
}

我假设以下架构：

CREATE TABLE PostLikes
(
    LikeId INT IDENTITY(1,1) PRIMARY KEY,
    PostId INT,
    UserId INT
)

而且我假设您想使用postId, userid组合“切换”插入或删除行。

于 2015-04-07T05:34:19.893 回答