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 # Class EquationAPI

 Last update: 16.07.2025 

Namespace: [VM.API.Pre](VM.API.Pre.md)  
Assembly: VM.API.Pre.dll

```csharp
public static class EquationAPI

```

#### Inheritance

[object](https://learn.microsoft.com/dotnet/api/system.object) ← [EquationAPI](VM.API.Pre.EquationAPI.md)

#### Extension Methods

[LinkPropertyItemCache.GetLinkProperties(object, LinkPropertyType)](VM.Models.Pre.Cache.LinkPropertyItemCache.md#VM_Models_Pre_Cache_LinkPropertyItemCache_GetLinkProperties_System_Object_VM_Models_Pre_LinkPropertyType_), [LinkPropertyItemCache.GetLinkPropertiesAndValues(object, LinkPropertyType)](VM.Models.Pre.Cache.LinkPropertyItemCache.md#VM_Models_Pre_Cache_LinkPropertyItemCache_GetLinkPropertiesAndValues_System_Object_VM_Models_Pre_LinkPropertyType_), [LinkPropertyItemCache.GetLinkedObjects<T>(object, LinkPropertyType)](VM.Models.Pre.Cache.LinkPropertyItemCache.md#VM_Models_Pre_Cache_LinkPropertyItemCache_GetLinkedObjects__1_System_Object_VM_Models_Pre_LinkPropertyType_)

## Methods

### CreateFirstOrderDifferentialEquation(SubSystemDocument, FunctionEquType, Obj, ExpressionValueVariable?, string, SymmetricType)

Create .

```csharp
[NotNull(new string[] { "document" })]
[NotNullObj(new string[] { "function" })]
public static Obj CreateFirstOrderDifferentialEquation(this SubSystemDocument document, EquationFunctionDiff.FunctionEquType diffType, Obj function, ExpressionValueVariable? initialDisp = null, string name = "", SymmetricType symmetricType = SymmetricType.None)

```

#### Parameters

`document` SubSystemDocument

The document to create the 1st differential equation.

`diffType` EquationFunctionDiff.FunctionEquType

The solving method type of the 1st differential equation.

`function` [Obj](VM.API.Pre.Obj.md)

The function of the 1st differential equation.

`initialDisp` ExpressionValueVariable?

The initial displacement of the 1st differential equation.

`name` [string](https://learn.microsoft.com/dotnet/api/system.string)

The name of the 1st differential equation.

`symmetricType` SymmetricType

The symmetric type of the new

#### Returns

[Obj](VM.API.Pre.Obj.md)

The new  object that is created by this API.

#### Exceptions

[ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception)

Will be thrown if 'document', 'function' argument is null.

[ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception)

Will be thrown if 'function' is not equal to  and .

### CreateSecondOrderDifferentialEquation(SubSystemDocument, FunctionEquType, Obj, ExpressionValueVariable?, ExpressionValueVariable?, string, SymmetricType)

Create .

```csharp
[NotNull(new string[] { "document" })]
[NotNullObj(new string[] { "function" })]
public static Obj CreateSecondOrderDifferentialEquation(this SubSystemDocument document, EquationFunctionDiff.FunctionEquType diffType, Obj function, ExpressionValueVariable? initialDisp = null, ExpressionValueVariable? initialVel = null, string name = "", SymmetricType symmetricType = SymmetricType.None)

```

#### Parameters

`document` SubSystemDocument

The document to create the 2nd differential equation.

`diffType` EquationFunctionDiff.FunctionEquType

The solving method type of the 2nd differential equation.

`function` [Obj](VM.API.Pre.Obj.md)

The function of the 2nd differential equation.

`initialDisp` ExpressionValueVariable?

The initial displacement of the 2nd differential equation.

`initialVel` ExpressionValueVariable?

The initial velocity of the 2nd differential equation.

`name` [string](https://learn.microsoft.com/dotnet/api/system.string)

The name of the 2nd differential equation.

`symmetricType` SymmetricType

The symmetric type of the new

#### Returns

[Obj](VM.API.Pre.Obj.md)

The new  object that is created by this API.

#### Exceptions

[ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception)

Will be thrown if 'document', 'function' argument is null.

[ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception)

Will be thrown if 'function' is not equal to  and .

### CreateVariableEquation(SubSystemDocument, Obj, ExpressionValueVariable?, string, SymmetricType)

Create .

```csharp
[NotNull(new string[] { "document" })]
[NotNullObj(new string[] { "function" })]
public static Obj CreateVariableEquation(this SubSystemDocument document, Obj function, ExpressionValueVariable? initialDisp = null, string name = "", SymmetricType symmetricType = SymmetricType.None)

```

#### Parameters

`document` SubSystemDocument

The document to create a variable equation.

`function` [Obj](VM.API.Pre.Obj.md)

The function of a variable equation.

`initialDisp` ExpressionValueVariable?

The initial displacement of a variable equation.

`name` [string](https://learn.microsoft.com/dotnet/api/system.string)

The name of a variable equation.

`symmetricType` SymmetricType

The symmetric type of the new

#### Returns

[Obj](VM.API.Pre.Obj.md)

The new  object that is created by this API.

#### Exceptions

[ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception)

Will be thrown if 'document', 'function' argument is null.

[ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception)

Will be thrown if 'function' is not equal to  and .