这看似微不足道,但我见过的每个ADO.net示例在“更新”之前几乎总是有“填充”。我们真的不想填充可能有1000个blob的数据集,我们只想添加(插入)到表中。是否需要填写更新?作为示例,这里是来自MSFT网站的示例代码(我们正在做类似的事情):
SqlConnection con = new SqlConnection("Server=Darkover;uid=<username>;pwd=<strong password>;database=northwind");
SqlDataAdapter da = new SqlDataAdapter("Select * From MyImages", con);
SqlCommandBuilder MyCB = new SqlCommandBuilder(da); // What does this even do?
DataSet ds = new DataSet("MyImages");
da.MissingSchemaAction = MissingSchemaAction.AddWithKey;
FileStream fs = new FileStream(@"C:\winnt\Gone Fishing.BMP", FileMode.OpenOrCreate, FileAccess.Read);
byte[] MyData= new byte[fs.Length];
fs.Read(MyData, 0, System.Convert.ToInt32(fs.Length));
fs.Close();
da.Fill(ds,"MyImages"); // are they really filling a dataset with all those images???
DataRow myRow;
myRow=ds.Tables["MyImages"].NewRow();
myRow["Description"] = "This would be description text";
myRow["imgField"] = MyData;
ds.Tables["MyImages"].Rows.Add(myRow);
da.Update(ds, "MyImages");
con.Close();
答案 0 :(得分:0)
您希望调用da.Fill()
以获取MyImages
表的架构。这样,在为列分配值时,您可以使用DataRow
调用返回的NewRow()
和正确的架构(列,键等)。
您可以通过设置SqlDataAdapter
告诉SqlDataAdapter.FillCommandBehavior
仅返回没有数据的架构:
da.FillCommandBehavior = CommandBehavior.SchemaOnly;
da.Fill(ds,"MyImages"); // Just get the schema for MyImages
DataRow myRow = ds.Tables["MyImages"].NewRow();
myRow["Description"] = "This would be description text";
myRow["imgField"] = MyData;
ds.Tables["MyImages"].Rows.Add(myRow);
da.Update(ds, "MyImages");
如果您的查询返回多个表,您也可以使用da.FillSchema()
,使用单个DataTable
或DataSet
。
DataTable dt = new DataTable();
da.FillSchema(dt, SchemaType.Mapped);
DataRow myRow = dt.NewRow();
myRow["Description"] = "This would be description text";
myRow["imgField"] = MyData;
dt.Rows.Add(myRow);
da.Update(dt);