DataTable sort retrieve merge and other operational instances in C

1. Sort
1. Get the default view of DataTable
2. Set the sort expression for the view
3. Replace DataTable with the new DataTable exported from the sorted view (Asc ascending can be omitted, multi-column sorting separated by ", ")
1) Regeneration method

dstaset.Tables.Add(dt)
dataset.Tables(0).DefaultView.Sort = "id desc"

2) Direct method

dv = New DataView(dt)
dv.Sort = "id desc"
dt = dv.ToTable();

3) Indirect method

dv = New DataView(ds.Tables[0])
dv.Sort = "id desc"
dt = dv.ToTable();

2. Retrieve

Set the query string
Use Select to get an array of all data row objects that meet the criteria (multiple query criteria separated by and)

DataRow[] matches = dt.Select("id<'003' and name=' The name 11'");
string strName = matches[0]["name"].ToString();

3. The merger

Suppose there are two DataTable:Dt1 and Dt2. Table structure 1 sample
This method can be used after attaching Dt2 to Dt1

dt1.Merge(dt2);

4. Query DataTable for issues that should be noted

After completing one query and returning one DataTable, there are many times when you want to continue searching in the query results. You can then re-query the results using the DataTable.Select method
The Select method has four overloads, and the one we often use is DataTable. Select(String)
The argument to String is qualified for the query. It is equivalent to the WHERE statement in SQL query language (excluding WHERE), whose syntax conforms to the SQL language syntax.
The Select method returns DataRow containing the data queried, but this DataRow is only one mapping of the queried DataTable, so DataRow changes with the rows of DataTable. For example, if DataTable's rows are deleted, so is the data in DataRow (even if Select was deleted first, then)
Therefore, in order to put the returned DataRow into the data display control, you need to put it into another DataTable. If you put the original DataTable directly or remove all the rows of the original DataTable before putting the data into the query, it will not work. The program will display an error saying "there is a row in the table".
In addition, inserting rows into a new table cannot be done directly in the DataTable.Rows.Add (DataRow) manner, as this would insert a new table and DataRow would be empty. To import rows, DataTable. ImportRow(DataRow). This assumes, of course, that the new table has the same structure as the original table 1.

Public Function SDEResearch(ByVal InputDT As DataTable, ByVal SearchStr As String) As DataTable
' Used to store the queried tables  
Dim ReSearchDT As DataTable = InputDT.Clone() ' Ensure that you have the same table structure as the source data table  
' Used to store returns from a query datarow An array of  
Dim ReSearchDR() As DataRow = Nothing 
Try 
ReSearchDR = InputDT.Select("NAME LIKE '%" + SearchStr + "%'") ' It's just mapped out from the table datarow() , so you cannot delete rows from the original table  
Catch ex As Exception 
Return Nothing 
End Try 
For i As Int16 = 0 To ReSearchDR.Length - 1 
ReSearchDT.ImportRow(ReSearchDR(i)) 
Next 
Return ReSearchDT 
End Function

Attachment: Methods for filtering DataTable data

Some methods of filtering DataTable Select,dataview
When you take a little bit of data out of the database and you want to put it together, it's easy to think:

DataTable dt = new DataTable();// Assuming that dt Is made up of "SELECT C1,C2,C3 FROM T1" The result of the query  
for (int i = 0; i < dt.Rows.Count; i++) 
{ 
    if (dt.Rows[i]["C1"].ToString() == "abc")// Query conditions  
    { 
        // operate  
    } 
}

But this kind of practice USES 1 to say twice also, use many tired. Is there a better way? Remember that LinQ can query DataTable directly. Is there a similar method in.Net Framework 2.0? The answer is yes, dt.Select().

DataRow[] drArr = dt.Select("C1='abc'");// The query 

You can also do this:

DataRow[] drArr = dt.Select("C1 LIKE 'abc%'");// Fuzzy query  
DataRow[] drArr = dt.Select("'abc' LIKE C1 + '%'", "C2 DESC");// On the other 1 A fuzzy query method  
DataRow[] drArr = dt.Select("C1='abc'", "C2 DESC");// The sorting 

Again, if you want to assign DataRow to the new DataTable, how do you assign it? You might think:

DataTable dtNew = dt.Clone(); 
for (int i = 0; i < drArr.Length; i++) 
{ 
    dtNew.Rows.Add(drArr[i]); 
}

But then the program will make a mistake and say that DataRow belongs to another DataTable. So how do you do that? It's very simple, and this solves it:

dv = New DataView(dt)
dv.Sort = "id desc"
dt = dv.ToTable();

0
And we're done.
DataRow[] in 3.5 has an extension of CopyToDataTable()

/* 
*  supplement 1 Next, you can use it DataView To achieve the purpose of retrieval.  
*/ 
DataTable dataSource = new DataTable(); 
DataView dv = dataSource.DefaultView; 
dv.RowFilter = "columnA = 'abc'"; 
//1. Directly obtained after filtering DataTable 
DataTable newTable1 = dv.ToTable(); 
//2. Set up the new DataTable the TableName 
DataTable newTable2 = dv.ToTable("NewTableName"); 
//3. Sets whether the new table filters duplicates , The column name of the owned column and the order in which it appears  
// That is, you can set the fields for the new table. But the field names are definitely old tables dataSource Owned by.  
DataTable newTable3 = 
dv.ToTable(true, new string[] { "columnA,columnF,columnC" }); 
//4. A combination of 2.3 At two o 'clock.  
DataTable newTable4 = 
dv.ToTable("NewTableName", true, new string[] { "columnA,columnF,columnC" });