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SqlBulkCopy.WriteToServerAsync(reader) fails to write after upgrading Microsoft.Data.SqlClient to 7.0.0 #4149
Description
Describe the bug
After upgrading the Microsoft.Data.SqlClient to 7.0.0, SqlBulkCopy.WriteToServerAsync(reader) fails to write, however the same code works fine without any changes in 6.1.4 version.
Cannot access destination table 'dbo.TestTable'.. A variable that has been assigned in a SELECT statement cannot be included in a expression or assignment when used in conjunction with a from clause
To reproduce
Below code tries to read from the table and writes to the similar table with the same schema.
CREATE TABLE [dbo].[TestTable]
(
Column1 varchar(255) NULL,
Column2 varchar(255) NOT NULL,
PRIMARY KEY NONCLUSTERED (TableName) NOT ENFORCED
) WITH (CLUSTERED COLUMNSTORE INDEX)
GO
var table = "dbo.TestTable";
var query = "select top 1 [Column1], [Column2] from [dbo].[TestTable]";
using (var command = new SqlCommand())
{
var sqlConnectionString = _connectionStringProvider.GetConnectionString();
var sourceSqlConnection = new SqlConnection(sqlConnectionString);
await sourceSqlConnection.OpenAsync();
command.Connection = sourceSqlConnection;
command.CommandTimeout = 3600;
command.CommandText = query;
using (var reader = command.ExecuteReader())
{
using var targetSqlConnection = new SqlConnection(sqlConnectionString);
targetSqlConnection.Open();
using (SqlBulkCopy sqlBulkCopy = new SqlBulkCopy(targetSqlConnection))
{
sqlBulkCopy.DestinationTableName = table;
await sqlBulkCopy.WriteToServerAsync(reader);
}
}
}Expected behavior
sqlBulkCopy.WriteToServerAsync(reader) should write the rows read from the source table or the query.
Further technical details
Microsoft.Data.SqlClient version: 7.0.0
.NET target: .Net 10
SQL Server version: Microsoft Azure SQL Data Warehouse - 10.0.31510.0
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[-]SqlBulkCopy.WriteToServerAsync(reader) fails to write[/-][+]SqlBulkCopy.WriteToServerAsync(reader) fails to write after upgrading Microsoft.Data.SqlClient to 7.0.0[/+]edwardneal commentedon Apr 8, 2026
It looks like this is the result of #3590, apologies. I shifted the metadata retrieval from running a static
SELECT * FROM [TargetTable]to building up a query using a column list using:STRING_AGGis available in Azure Synapse and SQL 2017+ and I think using this in the query would fix it. I'll test that shortly.Edit: I've just reproduced this when connecting to a dedicated SQL pool in Azure Synapse Analytics.
Bump the nuget-all group with 3 updates (#102)
Bump Microsoft.Data.SqlClient from 6.1.6 to 7.1.0 (#66)