AdoDotNetConnectionSupport.DeriveSchema Method

Derives the schema returned from a specified command, indicating the layout of items and blocks in a given data reader.

Namespace:  Microsoft.VisualStudio.Data.AdoDotNet
Assembly:  Microsoft.VisualStudio.Data (in Microsoft.VisualStudio.Data.dll)

Syntax

'Declaration
Public Overridable Function DeriveSchema ( _
    command As String, _
    commandType As Integer, _
    parameters As DataParameter(), _
    commandTimeout As Integer _
) As DataReader

public virtual DataReader DeriveSchema(
    string command,
    int commandType,
    DataParameter[] parameters,
    int commandTimeout
)

public:
virtual DataReader^ DeriveSchema(
    String^ command, 
    int commandType, 
    array<DataParameter^>^ parameters, 
    int commandTimeout
)

abstract DeriveSchema : 
        command:string * 
        commandType:int * 
        parameters:DataParameter[] * 
        commandTimeout:int -> DataReader  
override DeriveSchema : 
        command:string * 
        commandType:int * 
        parameters:DataParameter[] * 
        commandTimeout:int -> DataReader

public function DeriveSchema(
    command : String, 
    commandType : int, 
    parameters : DataParameter[], 
    commandTimeout : int
) : DataReader

Parameters

• command
  Type: System.String

  Data-source-specific command for which to derive the schema

• commandType
  Type: System.Int32

  Type of the indicated command, specifying how to interpret the contents of the command parameter.

• parameters
  Type: array<Microsoft.VisualStudio.Data.DataParameter[]

  Array of AdoDotNetParameter objects for the specified command type.

• commandTimeout
  Type: System.Int32

  Length of time, in seconds, to block the client before canceling the schema derivation and returning to the caller. A value of zero indicates infinite timeout; value of -1 indicates a provider default.

Return Value

Type: Microsoft.VisualStudio.Data.DataReader
Returns a DataReader object instance representing the command schema.

Remarks

The schema of the data reader returned by this method must follow a specific format. For each result that would be returned when executing the command, there should be a result in the data reader. Each of these results should contain blocks that describe the items that would be returned when executing the command. The description should contain the following items:

• Name (String): the name of the item.

• Ordinal (Int32): the position of the item.

• UserDataType (String): the user data type of the item (for example, "myType").

• NativeDataType (String): the native data type of the item (for example, "nvarchar").

• ProviderDataType (Int32): the provider data type of the item (for example, System.Data.DbType.StringFixedLength).

• FrameworkDataType (Type): the framework data type of the item (for example, System.Int32).

• Length (Int32): the maximum length of an item, if applicable.

• Precision (Int32): the precision of an item, if applicable.

• Scale (Int32): the scale of an item, if applicable.

• Nullable (Boolean): the nullability of an item.

Those items that a provider does not support (for example, some forms of the data type) should be present but set to nulla null reference (Nothing in Visual Basic).

.NET Framework Security

• Full trust for the immediate caller. This member cannot be used by partially trusted code. For more information, see Using Libraries from Partially Trusted Code.

See Also

Reference

AdoDotNetConnectionSupport Class

Microsoft.VisualStudio.Data.AdoDotNet Namespace

DeriveSchema