Entity Framework - How to check if table exists?
I can't add comment to previous post. I'm using SQL Compact and I don't know schema of the table. I'm using this code to check for table It's pretty the same that in previous post but It works for any table.
/// <summary>
/// Check if data table is exist in application
/// </summary>
/// <typeparam name="T">Class of data table to check</typeparam>
/// <param name="db">DB Object</param>
public static bool CheckTableExists<T>(this ModelLocker db) where T : class
{
try
{
db.Set<T>().Count();
return true;
}
catch (Exception)
{
return false;
}
}
Assumption: SQL Server
Catching any old exception when querying the DbSet
does not mean the table does not exist.
Querying a DbSet
where the table does not exist will throw an EntityCommandExecutionException
with an inner exception of type SqlException
. That inner exception has an ErrorNumber
property.
Error number 208 reads (source):
Invalid object name '%.*ls'.
An alternative method; it's not as efficient as Ladislav's, but it's not tied to SQL Server (edited to add Where clause to address performance issue):
bool CheckTableExists()
{
try
{
context.YourTable.Where(s => s.<yourKeyField> = <impossible value>).Count();
return true;
}
catch (Exception)
{
return false;
}
}
If you need to check existence of the table you must call custom SQL code:
bool exists = context.Database
.SqlQuery<int?>(@"
SELECT 1 FROM sys.tables AS T
INNER JOIN sys.schemas AS S ON T.schema_id = S.schema_id
WHERE S.Name = 'SchemaName' AND T.Name = 'TableName'")
.SingleOrDefault() != null;
Table name is defined by default as the name of DbSet
exposed on your derived context but the default name can be overriden either by fluent API's ToTable
method or Table
data annotation.
Doing this in the generic way is not something supposed in code first approach. That will require browsing metadata and manually explore to which table is the entity mapped - this can be pretty complex because entity can be mapped to multiple tables. Code first doesn't offer access to metadata. You must convert DbContext
to ObjectContext
and browse MetadataWorkspace
.
Edit:
To convert DbContext
to ObjectContext
use this:
ObjectContext objContext = ((IObjectContextAdapter)dbContext).ObjectContext;