Open Method

EntityConnection.Open Method ()


Establishes a connection to the data source by calling the underlying data provider's Open method.

Namespace:   System.Data.EntityClient
Assembly:  System.Data.Entity (in System.Data.Entity.dll)

public override void Open()

Exception Condition

An error occurs when you open the connection, or the name of the underlying data provider is not known.


The inline connection string contains an invalid Metadata keyword value.

To avoid inadvertently putting objects such as System.Data.Common.CommandTrees and ObjectContext out of sync with their metadata, EntityConnection must lock its metadata. No changes to the connection string are allowed after the metadata is locked. The following are two scenarios in which metadata is locked:

  • The EntityConnection instance is constructed through the default constructor, or through the EntityConnection(String) constructor, which accepts a connection string. In either case the connection string might be changed multiple times before the connection is opened. Calling M:System.Data.EntityClient.EntityConnection.Open() or M:System.Data.EntityClient.EntityConnection.GetMetadataWorkspace() locks the metadata.

  • The EntityConnection instance is constructed through the EntityConnection(MetadataWorkspace, DbConnection) constructor, which that accepts a MetadataWorkspace and a DbConnection. In this case the metadata is locked at construction time. No changes to the connection string are ever allowed.

When metadata is loaded, the EntityConnection verifies that the conceptual model, the storage model, and the mapping file are all present.

.NET Framework
Available since 3.5
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