Dapper official translation Tutorial 5: QueryFirstOrDefault Dapper method of (turn)

Dapper official translation Tutorial 5: QueryFirstOrDefault Dapper method of

February 28, 2019 10:28:31  Day_and_Night_2017  Reads: 303

 

QueryFirstOrDefault method described

 

QueryFirstOrDefault method is an extension method, it can be called IDbConnection object, you can execute a query, and mapped to the result. If only one value, this value is returned directly, if there is no value, return to the default value, if more than one value, returns the first value.

You can be mapped type:

• Anonymous (anonymous type var)
• Strongly Typed (strongly typed)

 

The method may be used parameter QueryFirstOrDefault

 

Name	Description
sql	check sentence
param	parameter
transaction	Whether to open the transaction
commandTimeout	Timeout period
commandType	Command Type

 

Anonymous types query

 

string sql = "SELECT * FROM OrderDetails WHERE OrderDetailID = @OrderDetailID;";

using (var connection = new SqlCeConnection("Data Source=SqlCe_W3Schools.sdf"))
{
var orderDetail = connection.QueryFirstOrDefault(sql, new {OrderDetailID = 1});

FiddleHelper.WriteTable(orderDetail);
}

 

Strongly typed queries

 

string sql = "SELECT * FROM OrderDetails WHERE OrderDetailID = @OrderDetailID;";

using (var connection = new SqlCeConnection("Data Source=SqlCe_W3Schools.sdf"))
{
var orderDetail = connection.QueryFirstOrDefault<OrderDetail>(sql, new {OrderDetailID = 1});

FiddleHelper.WriteTable( new List<OrderDetail>() { orderDetail });
}