SqlCeCommand.Prepare 方法

會在資料來源上建立命令的備製 (或已編譯的) 版本。

命名空間：  System.Data.SqlServerCe
組件：  System.Data.SqlServerCe (在 System.Data.SqlServerCe.dll 中)

語法

'宣告
Public Overrides Sub Prepare
'用途
Dim instance As SqlCeCommand

instance.Prepare()

public override void Prepare()

public:
virtual void Prepare() override

abstract Prepare : unit -> unit 
override Prepare : unit -> unit 

public override function Prepare()

實作

IDbCommand.Prepare()

例外狀況

備註

如果 CommandType 屬性設定為 TableDirect，Prepare 不會執行任何作業。

在您呼叫 Prepare 之前，請在陳述式中指定每個參數的資料類型以做準備。針對每一個有可變長度資料類型的參數，您必須將 Size 屬性設定為所需要的最大值。如果條件不符合，則 Prepare 會傳回錯誤。

如果在呼叫 Prepare 之後呼叫 Execute 方法，則任何大於 Size 屬性指定值的參數值會自動被截斷成參數的原始指定大小，並且不會傳回任何截斷錯誤。

範例

Dim conn As New SqlCeConnection("Data Source = MyDatabase.sdf;")
conn.Open()

Dim command As SqlCeCommand = conn.CreateCommand()

' Create and prepare a SQL statement
'
command.CommandText = "INSERT INTO Region (RegionID, RegionDescription) VALUES (@id, @desc)"

Dim param As SqlCeParameter = Nothing

' NOTE:
' For optimal performance, make sure you always set the parameter
' type and the maximum size - this is especially important for non-fixed
' types such as NVARCHAR or NTEXT; In case of named parameters, 
' SqlCeParameter instances do not need to be added to the collection
' in the order specified in the query; If however you use ? as parameter
' specifiers, then you do need to add the parameters in the correct order
'
param = New SqlCeParameter("@id", SqlDbType.Int)
command.Parameters.Add(param)

param = New SqlCeParameter("@desc", SqlDbType.NVarChar, 100)
command.Parameters.Add(param)

command.Parameters("@desc").Size = 100

' Calling Prepare after having set the CommandText and parameters
'
command.Prepare()

' Execute the SQL statement
'
command.ExecuteNonQuery()

' Change parameter values and call ExecuteNonQuery again
'
command.Parameters(0).Value = 21
command.Parameters(1).Value = "mySecondRegion"
command.ExecuteNonQuery()

SqlCeConnection conn = new SqlCeConnection("Data Source = MyDatabase.sdf;");
conn.Open();

SqlCeCommand command = conn.CreateCommand();

// Create and prepare a SQL statement
//
command.CommandText = "INSERT INTO Region (RegionID, RegionDescription) VALUES (@id, @desc)";

SqlCeParameter param = null;

// NOTE:
// For optimal performance, make sure you always set the parameter
// type and the maximum size - this is especially important for non-fixed
// types such as NVARCHAR or NTEXT; In case of named parameters, 
// SqlCeParameter instances do not need to be added to the collection
// in the order specified in the query; If however you use ? as parameter
// specifiers, then you do need to add the parameters in the correct order
//
param = new SqlCeParameter("@id", SqlDbType.Int);
command.Parameters.Add(param);

param = new SqlCeParameter("@desc", SqlDbType.NVarChar, 100);
command.Parameters.Add(param);

command.Parameters["@desc"].Size = 100;

// Calling Prepare after having set the CommandText and parameters
//
command.Prepare();

// Execute the SQL statement
//
command.ExecuteNonQuery();

// Change parameter values and call ExecuteNonQuery again
//
command.Parameters[0].Value = 21;
command.Parameters[1].Value = "mySecondRegion";
command.ExecuteNonQuery();

請參閱

參考

SqlCeCommand 類別

System.Data.SqlServerCe 命名空間