Convert String to Int in EF 4.0
If you are using EFv4 + EDMX you can create custom model defined function which will do the CAST for you. You can then use that function in Linq-to-entities queries.
Jeff
Updated on June 06, 2022Comments
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Jeff about 2 years
Is there any way of doing this at all? I have a string field in the DB and I want to parse it into a int property in my LINQ query (yes, it must be at the IQueryable level, not in memory).
I know 2 years ago EF 1.0 couldn't do this (even though LINQ to SQL supported this basic functionality out of the box)...but I'm just wondering if anyone has come up with a way of doing this at this point?
Custom function mappings? Special syntax? Anything at all....
UPDATE:
I tried a model defined function as follows:
<Function Name="ConvertToInt32" ReturnType="Edm.Int32"> <Parameter Name="v" Type="Edm.String" /> <DefiningExpression> CAST(v AS INT) </DefiningExpression> </Function> [EdmFunction("Model.Repository", "ConvertToInt32")] public static int ConvertToInt32(string value) { throw new InvalidOperationException("Only valid when used as part of a LINQ query."); }
but it doesn't seem to work. I get the runtime exception:
ErrorDescription=Type 'INT' could not be found. Make sure that the required schemas are loaded and that the namespaces are imported correctly. StackTrace: at System.Data.Common.EntitySql.SemanticAnalyzer.ConvertTypeName(Node typeName, SemanticResolver sr) at System.Data.Common.EntitySql.SemanticAnalyzer.ConvertTypeExprArgs(BuiltInExpr astBuiltInExpr, SemanticResolver sr) at System.Data.Common.EntitySql.SemanticAnalyzer.<CreateBuiltInExprConverter>b__73(BuiltInExpr bltInExpr, SemanticResolver sr) at System.Data.Common.EntitySql.SemanticAnalyzer.ConvertBuiltIn(Node astExpr, SemanticResolver sr) at System.Data.Common.EntitySql.SemanticAnalyzer.Convert(Node astExpr, SemanticResolver sr) at System.Data.Common.EntitySql.SemanticAnalyzer.ConvertValueExpression(Node astExpr, SemanticResolver sr) at System.Data.Common.EntitySql.SemanticAnalyzer.ConvertQueryStatementToDbExpression(Statement astStatement, SemanticResolver sr) at System.Data.Common.EntitySql.SemanticAnalyzer.AnalyzeQueryCommand(Node astExpr) at System.Data.Common.EntitySql.CqlQuery.<AnalyzeQueryExpressionSemantics>b__8(SemanticAnalyzer analyzer, Node astExpr) at System.Data.Common.EntitySql.CqlQuery.AnalyzeSemanticsCommon[TResult](Node astExpr, Perspective perspective, ParserOptions parserOptions, IEnumerable`1 parameters, IEnumerable`1 variables, Func`3 analysisFunction) at System.Data.Common.EntitySql.CqlQuery.AnalyzeQueryExpressionSemantics(Node astQueryCommand, Perspective perspective, ParserOptions parserOptions, IEnumerable`1 parameters, IEnumerable`1 variables) at System.Data.Common.EntitySql.CqlQuery.<>c__DisplayClass4.<CompileQueryCommandLambda>b__3(Node astCommand, ParserOptions validatedParserOptions) at System.Data.Common.EntitySql.CqlQuery.CompileCommon[TResult](String commandText, Perspective perspective, ParserOptions parserOptions, Func`3 compilationFunction) at System.Data.Common.EntitySql.CqlQuery.CompileQueryCommandLambda(String queryCommandText, Perspective perspective, ParserOptions parserOptions, IEnumerable`1 parameters, IEnumerable`1 variables) at System.Data.Mapping.ViewGeneration.Utils.ExternalCalls.CompileFunctionDefinition(String functionFullName, String functionDefinition, IList`1 functionParameters, EdmItemCollection edmItemCollection) at System.Data.Metadata.Edm.EdmItemCollection.GenerateFunctionDefinition(EdmFunction function) at System.Data.Common.Utils.Memoizer`2.<>c__DisplayClass2.<Evaluate>b__0() at System.Data.Common.Utils.Memoizer`2.Result.GetValue() at System.Data.Common.Utils.Memoizer`2.Evaluate(TArg arg) at System.Data.Metadata.Edm.EdmItemCollection.GetGeneratedFunctionDefinition(EdmFunction function) at System.Data.Metadata.Edm.MetadataWorkspace.GetGeneratedFunctionDefinition(EdmFunction function) at System.Data.Query.PlanCompiler.ITreeGenerator.Visit(DbFunctionExpression e) InnerException:
UPDATE: I got it to work as follows
<Function Name="ConvertToInt32" ReturnType="Edm.Int32"> <Parameter Name="v" Type="Edm.String" /> <DefiningExpression> CAST(v AS Edm.Int32) </DefiningExpression> </Function>
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Jeff about 13 yearsAny way to add this to the MetadataWorkspace at runtime? Ideally I'd like the Convert.ToInt32 to perform this function. Thanks!
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Jeff about 13 yearsI tried this and it doesn't seem to work: see updated question.
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Ladislav Mrnka about 13 yearsThe question about adding this to metadata workspace at runtime is very good but I don't know the answer for that. Anyway you will not be able to map it to
Convert.ToInt32
because you can't addEdmFunction
attribute to that method.