problem search primary key field in sqlite database

[Paul]

I am using vb.net sqlite.net and dblinq0.20.1 to search a sqlite table
on a primary key field.

My code looks like this

Dim blb = (From d In db.Data Where d.UID = myuid Select d).Single
This returns the error "Coalesce used with type that cannot be null"

If I search on a nullable field it works fine.

Anyone come across this error before and throw any light on what the
issue is?

In the watch window, the stack trace has

StackTrace " at
System.Linq.Expressions.Expression.ValidateCoalesceArgTypes(Type left,
Type right) at
System.Linq.Expressions.Expression.Coalesce(Expression left,
Expression right) at
DbLinq.Data.Linq.Sugar.ExpressionMutator.Implementation.BinaryExpressionMutator.Mutate(IList`1
operands) in mypath\Visual Studio 2010\Projects\DbLinq-0.20.1\src
\DbLinq\Data\Linq\Sugar\ExpressionMutator\Implementation
\BinaryExpressionMutator.cs:line 160 at
DbLinq.Data.Linq.Sugar.ExpressionMutator.ExpressionMutatorExtensions.ChangeOperands[T]
(T expression, IList`1 operands, Boolean checkForChanges) in mypath
\Visual Studio 2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq\Sugar
\ExpressionMutator\ExpressionMutatorExtensions.cs:line 70 at
DbLinq.Data.Linq.Sugar.ExpressionMutator.ExpressionMutatorExtensions.ChangeOperands[T]
(T expression, IList`1 operands) in mypath\Visual Studio 2010\Projects
\DbLinq-0.20.1\src\DbLinq\Data\Linq\Sugar\ExpressionMutator
\ExpressionMutatorExtensions.cs:line 107 at
DbLinq.Data.Linq.Sugar.Implementation.ExpressionDispatcher.AnalyzeOperator(Expression
expression, BuilderContext builderContext) in mypath\Visual Studio
2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq\Sugar\Implementation
\ExpressionDispatcher.Analyzer.cs:line 1112 at
DbLinq.Data.Linq.Sugar.Implementation.ExpressionDispatcher.Analyze(Expression
expression, IList`1 parameters, BuilderContext builderContext) in
mypath\Visual Studio 2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq
\Sugar\Implementation\ExpressionDispatcher.Analyzer.cs:line 153 at
DbLinq.Data.Linq.Sugar.Implementation.ExpressionDispatcher.Analyze(Expression
expression, BuilderContext builderContext) in mypath\Visual Studio
2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq\Sugar\Implementation
\ExpressionDispatcher.Analyzer.cs:line 101 at
DbLinq.Data.Linq.Sugar.Implementation.ExpressionDispatcher.AnalyzeLambda(Expression
expression, IList`1 parameters, BuilderContext builderContext) in
mypath\Visual Studio 2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq
\Sugar\Implementation\ExpressionDispatcher.Analyzer.cs:line 713 at
DbLinq.Data.Linq.Sugar.Implementation.ExpressionDispatcher.Analyze(Expression
expression, IList`1 parameters, BuilderContext builderContext) in
mypath\Visual Studio 2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq
\Sugar\Implementation\ExpressionDispatcher.Analyzer.cs:line 111 at
DbLinq.Data.Linq.Sugar.Implementation.ExpressionDispatcher.AnalyzeQuote(Expression
piece, IList`1 parameters, BuilderContext builderContext) in mypath
\Visual Studio 2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq\Sugar
\Implementation\ExpressionDispatcher.Analyzer.cs:line 1072 at
DbLinq.Data.Linq.Sugar.Implementation.ExpressionDispatcher.Analyze(Expression
expression, IList`1 parameters, BuilderContext builderContext) in
mypath\Visual Studio 2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq
\Sugar\Implementation\ExpressionDispatcher.Analyzer.cs:line 115 at
DbLinq.Data.Linq.Sugar.Implementation.ExpressionDispatcher.Analyze(Expression
expression, Expression parameter, BuilderContext builderContext) in
mypath\Visual Studio 2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq
\Sugar\Implementation\ExpressionDispatcher.Analyzer.cs:line 96 at
DbLinq.Data.Linq.Sugar.Implementation.ExpressionDispatcher.AnalyzeWhere(IList`1
parameters, BuilderContext builderContext) in mypath\Visual Studio
2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq\Sugar\Implementation
\ExpressionDispatcher.Analyzer.cs:line 686 at
DbLinq.Data.Linq.Sugar.Implementation.ExpressionDispatcher.AnalyzeQueryableCall(MethodInfo
method, IList`1 parameters, BuilderContext builderContext) in mypath
\Visual Studio 2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq\Sugar
\Implementation\ExpressionDispatcher.Analyzer.cs:line 251 at
DbLinq.Data.Linq.Sugar.Implementation.ExpressionDispatcher.AnalyzeCall(MethodCallExpression
expression, IList`1 parameters, BuilderContext builderContext) in
mypath\Visual Studio 2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq
\Sugar\Implementation\ExpressionDispatcher.Analyzer.cs:line 178 at
DbLinq.Data.Linq.Sugar.Implementation.ExpressionDispatcher.Analyze(Expression
expression, IList`1 parameters, BuilderContext builderContext) in
mypath\Visual Studio 2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq
\Sugar\Implementation\ExpressionDispatcher.Analyzer.cs:line 109 at
DbLinq.Data.Linq.Sugar.Implementation.ExpressionDispatcher.Analyze(Expression
expression, Expression parameter, BuilderContext builderContext) in
mypath\Visual Studio 2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq
\Sugar\Implementation\ExpressionDispatcher.Analyzer.cs:line 96 at
DbLinq.Data.Linq.Sugar.Implementation.ExpressionDispatcher.Analyze(ExpressionChain
expressions, Expression parameter, BuilderContext builderContext) in
mypath\Visual Studio 2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq
\Sugar\Implementation\ExpressionDispatcher.Analyzer.cs:line 73 at
DbLinq.Data.Linq.Sugar.Implementation.QueryBuilder.BuildExpressionQuery(ExpressionChain
expressions, Expression tableExpression, BuilderContext
builderContext) in mypath\Visual Studio 2010\Projects\DbLinq-0.20.1\src
\DbLinq\Data\Linq\Sugar\Implementation\QueryBuilder.cs:line 203 at
DbLinq.Data.Linq.Sugar.Implementation.QueryBuilder.BuildExpressionQuery(ExpressionChain
expressions, BuilderContext builderContext) in mypath\Visual Studio
2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq\Sugar\Implementation
\QueryBuilder.cs:line 182 at
DbLinq.Data.Linq.Sugar.Implementation.QueryBuilder.BuildExpressionQuery(ExpressionChain
expressions, QueryContext queryContext) in mypath\Visual Studio
2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq\Sugar\Implementation
\QueryBuilder.cs:line 76 at
DbLinq.Data.Linq.Sugar.Implementation.QueryBuilder.GetSelectQuery(ExpressionChain
expressions, QueryContext queryContext) in mypath\Visual Studio
2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq\Sugar\Implementation
\QueryBuilder.cs:line 393 at
DbLinq.Data.Linq.Implementation.QueryProvider`1.GetQuery(Expression
expression) in mypath\Visual Studio 2010\Projects\DbLinq-0.20.1\src
\DbLinq\Data\Linq\Implementation\QueryProvider.cs:line 165 at
DbLinq.Data.Linq.Implementation.QueryProvider`1.GetEnumerator() in
mypath\Visual Studio 2010\Projects\DbLinq-0.20.1\src\DbLinq\Data\Linq
\Implementation\QueryProvider.cs:line 215 at
System.Linq.SystemCore_EnumerableDebugView`1.get_Items()" String